repo/luan: docs/manual.html comparison

comparison docs/manual.html @ 243:c912f6de2053

more work on the manual git-svn-id: https://luan-java.googlecode.com/svn/trunk@244 21e917c8-12df-6dd8-5cb6-c86387c605b9

author	fschmidt@gmail.com <fschmidt@gmail.com@21e917c8-12df-6dd8-5cb6-c86387c605b9>
date	Wed, 08 Oct 2014 06:22:04 +0000
parents	b5a926c481a5
children

comparison

equal deleted inserted replaced

-:b5a926c481a5
+:c912f6de2053
 <LI><A HREF="#3.3.3">3.3.3 &ndash; Assignment</A>
 <LI><A HREF="#3.3.4">3.3.4 &ndash; Control Structures</A>
 <LI><A HREF="#3.3.5">3.3.5 &ndash; For Statement</A>
 <LI><A HREF="#3.3.6">3.3.6 &ndash; Function Calls as Statements</A>
 <LI><A HREF="#3.3.7">3.3.7 &ndash; Local Declarations</A>
+<LI><A HREF="#3.3.8">3.3.8 &ndash; Or/And Statements</A>
 </UL>
 <LI><A HREF="#3.4">3.4 &ndash; Expressions</A>
 <UL>
 <LI><A HREF="#3.4.1">3.4.1 &ndash; Arithmetic Operators</A>
 <LI><A HREF="#3.4.2">3.4.2 &ndash; Coercion</A>
 </UL>
 <LI><A HREF="#3.5">3.5 &ndash; Visibility Rules</A>
 </UL>
 <P>
 <LI><A HREF="#4">4 &ndash; The Application Program Interface</A>
-<UL>
-<LI><A HREF="#4.1">4.1 &ndash; The Stack</A>
-<LI><A HREF="#4.2">4.2 &ndash; Stack Size</A>
-<LI><A HREF="#4.3">4.3 &ndash; Valid and Acceptable Indices</A>
-<LI><A HREF="#4.4">4.4 &ndash; C Closures</A>
-<LI><A HREF="#4.5">4.5 &ndash; Registry</A>
-<LI><A HREF="#4.6">4.6 &ndash; Error Handling in C</A>
-<LI><A HREF="#4.7">4.7 &ndash; Handling Yields in C</A>
-<LI><A HREF="#4.8">4.8 &ndash; Functions and Types</A>
-<LI><A HREF="#4.9">4.9 &ndash; The Debug Interface</A>
-</UL>
 <P>
 <LI><A HREF="#5">5 &ndash; The Auxiliary Library</A>
-<UL>
-<LI><A HREF="#5.1">5.1 &ndash; Functions and Types</A>
-</UL>
 <P>
 <LI><A HREF="#6">6 &ndash; Standard Libraries</A>
 <UL>
 <LI><A HREF="#6.1">6.1 &ndash; Basic Functions</A>
 <LI><A HREF="#6.2">6.2 &ndash; Coroutine Manipulation</A>
 </UL>
 <h1>1 &ndash; <a name="1">Introduction</a></h1>
-<p>
+<p>Luan is a high level programming language based on <a href="http://www.lua.org">Lua</a>.  A great strength of Lua is its simplicity and Luan takes this even further, being even simpler than Lua.  The goal is to provide a simple programming language for the casual programmer with as few concepts as possible so that programmers can quickly learn the language and then easily understand any code written in Luan.
-Lua is an extension programming language designed to support
-general procedural programming with data description
+<p>Luan is implemented in Java and is tightly coupled with Java.  So it makes a great scripting language for Java programmers.  By importing the <em>Java</em> package, one can directly call Java from Luan.
-facilities.
-It also offers good support for object-oriented programming,
+<p>Unlike Lua which is meant to be embedded, Luan is meant to be a full scripting language.  This done not by adding feature to Luan, but rather by providing a complete set of libraries.
-functional programming, and data-driven programming.
-Lua is intended to be used as a powerful, lightweight,
-embeddable scripting language for any program that needs one.
-Lua is implemented as a library, written in <em>clean C</em>,
-the common subset of Standard&nbsp;C and C++.
-<p>
-Being an extension language, Lua has no notion of a "main" program:
-it only works <em>embedded</em> in a host client,
-called the <em>embedding program</em> or simply the <em>host</em>.
-The host program can invoke functions to execute a piece of Lua code,
-can write and read Lua variables,
-and can register C&nbsp;functions to be called by Lua code.
-Through the use of C&nbsp;functions, Lua can be augmented to cope with
-a wide range of different domains,
-thus creating customized programming languages sharing a syntactical framework.
-The Lua distribution includes a sample host program called <code>lua</code>,
-which uses the Lua library to offer a complete, standalone Lua interpreter,
-for interactive or batch use.
-<p>
-Lua is free software,
-and is provided as usual with no guarantees,
-as stated in its license.
-The implementation described in this manual is available
-at Lua's official web site, <code>www.lua.org</code>.
-<p>
-Like any other reference manual,
-this document is dry in places.
-For a discussion of the decisions behind the design of Lua,
-see the technical papers available at Lua's web site.
-For a detailed introduction to programming in Lua,
-see Roberto's book, <em>Programming in Lua</em>.
 <h1>2 &ndash; <a name="2">Basic Concepts</a></h1>
 <p>
 This section describes the basic concepts of the language.
 <h2>2.1 &ndash; <a name="2.1">Values and Types</a></h2>
 <p>
-Lua is a <em>dynamically typed language</em>.
+Luan is a <em>dynamically typed language</em>.
 This means that
 variables do not have types; only values do.
 There are no type definitions in the language.
 All values carry their own type.
 <p>
-All values in Lua are <em>first-class values</em>.
+All values in Luan are <em>first-class values</em>.
 This means that all values can be stored in variables,
 passed as arguments to other functions, and returned as results.
 <p>
 There are eight basic types in Lua:
 <em>nil</em>, <em>boolean</em>, <em>number</em>,
-<em>string</em>, <em>function</em>, <em>userdata</em>,
+<em>string</em>, <em>binary</em>, <em>function</em>, <em>userdata</em>,
-<em>thread</em>, and <em>table</em>.
+and <em>table</em>.
 <em>Nil</em> is the type of the value <b>nil</b>,
 whose main property is to be different from any other value;
 it usually represents the absence of a useful value.
+<em>Nil</em> is implemented as the Java value <em>null</em>.
 <em>Boolean</em> is the type of the values <b>false</b> and <b>true</b>.
-Both <b>nil</b> and <b>false</b> make a condition false;
+<em>Boolean</em> is implemented as the Java class <em>Boolean</em>.
-any other value makes it true.
 <em>Number</em> represents real (double-precision floating-point) numbers.
-Operations on numbers follow the same rules of
+<em>Number</em> is implemented as the Java class <em>Number</em>.  Any Java subclass of <em>Number</em> is allowed and this is invisible to the Luan user.  Operations on numbers follow the same rules of
-the underlying C&nbsp;implementation,
+the underlying Java&nbsp;implementation.
-which, in turn, usually follows the IEEE 754 standard.
-(It is easy to build Lua interpreters that use other
+<em>String</em> is implemented as the Java class <em>String</em>.
-internal representations for numbers,
+<em>Binary</em> is implemented as the Java type <em>byte[]</em>.
-such as single-precision floats or long integers;
-see file <code>luaconf.h</code>.)
-<em>String</em> represents immutable sequences of bytes.
+<p>
+Luan can call (and manipulate) functions written in Luan and
-Lua is 8-bit clean:
+functions written in Java
-strings can contain any 8-bit value,
-including embedded zeros ('<code>\0</code>').
-<p>
-Lua can call (and manipulate) functions written in Lua and
-functions written in C
 (see <a href="#3.4.9">&sect;3.4.9</a>).
 <p>
-The type <em>userdata</em> is provided to allow arbitrary C&nbsp;data to
+The type <em>userdata</em> is provided to allow arbitrary Java&nbsp;objects to
 be stored in Lua variables.
-A userdata value is a pointer to a block of raw memory.
+A userdata value is a Java object that isn't of the standard Luan types.
-There are two kinds of userdata:
-full userdata, where the block of memory is managed by Lua,
-and light userdata, where the block of memory is managed by the host.
+<p>
-Userdata has no predefined operations in Lua,
+Lua has a type <em>thread</em> that Luan lacks because Luan does not have the Lua concept of coroutines.
-except assignment and identity test.
-By using <em>metatables</em>,
-the programmer can define operations for full userdata values
-(see <a href="#2.4">&sect;2.4</a>).
-Userdata values cannot be created or modified in Lua,
-only through the C&nbsp;API.
-This guarantees the integrity of data owned by the host program.
-<p>
-The type <em>thread</em> represents independent threads of execution
-and it is used to implement coroutines (see <a href="#2.6">&sect;2.6</a>).
-Do not confuse Lua threads with operating-system threads.
-Lua supports coroutines on all systems,
-even those that do not support threads.
 <p>
 The type <em>table</em> implements associative arrays,
 that is, arrays that can be indexed not only with numbers,
-but with any Lua value except <b>nil</b> and NaN
+but with any Lua value except <b>nil</b>.
-(<em>Not a Number</em>, a special numeric value used to represent
-undefined or unrepresentable results, such as <code>0/0</code>).
 Tables can be <em>heterogeneous</em>;
 that is, they can contain values of all types (except <b>nil</b>).
 Any key with value <b>nil</b> is not considered part of the table.
 Conversely, any key that is not part of a table has
 an associated value <b>nil</b>.
 if and only if <code>i</code> and <code>j</code> are raw equal
 (that is, equal without metamethods).
 <p>
-Tables, functions, threads, and (full) userdata values are <em>objects</em>:
+Tables, functions, and userdata values are <em>objects</em>:
 variables do not actually <em>contain</em> these values,
 only <em>references</em> to them.
 Assignment, parameter passing, and function returns
 always manipulate references to such values;
 these operations do not imply any kind of copy.
 Any table used as the value of <code>_ENV</code> is called an <em>environment</em>.
 <p>
 Lua keeps a distinguished environment called the <em>global environment</em>.
-This value is kept at a special index in the C registry (see <a href="#4.5">&sect;4.5</a>).
+This value is kept in the Luan state implemented in Java.
-In Lua, the variable <a href="#pdf-_G"><code>_G</code></a> is initialized with this same value.
+In Luan, the variable <a href="#pdf-_G"><code>_G</code></a> is initialized with this same value.
 <p>
 When Lua compiles a chunk,
-it initializes the value of its <code>_ENV</code> upvalue
+it initializes the value of its <code>_ENV</code> to an empty table.
-with the global environment (see <a href="#pdf-load"><code>load</code></a>).
+The values in the global environment become local variables of the chunk.
-Therefore, by default,
+All standard libraries are loaded in the global environment
-global variables in Lua code refer to entries in the global environment.
+and so they become available as local variables.
-Moreover, all standard libraries are loaded in the global environment
+You can use <a href="#pdf-load"><code>load</code></a> (or <a href="#pdf-loadfile"><code>load_file</code></a>)
-and several functions there operate on that environment.
+to load a chunk with a specific environment instead of starting empty.
-You can use <a href="#pdf-load"><code>load</code></a> (or <a href="#pdf-loadfile"><code>loadfile</code></a>)
-to load a chunk with a different environment.
-(In C, you have to load the chunk and then change the value
+<p>
-of its first upvalue.)
+If you change the values in the global environment,
-<p>
-If you change the global environment in the registry
-(through C code or the debug library),
 all chunks loaded after the change will get the new environment.
 Previously loaded chunks are not affected, however,
-as each has its own reference to the environment in its <code>_ENV</code> variable.
+as each has its own references to the values in its local variables.
 Moreover, the variable <a href="#pdf-_G"><code>_G</code></a>
 (which is stored in the original global environment)
 is never updated by Lua.
 <h2>2.3 &ndash; <a name="2.3">Error Handling</a></h2>
 <p>
-Because Lua is an embedded extension language,
+Luan error handling is quite different from Lua.
-all Lua actions start from C&nbsp;code in the host program
-calling a function from the Lua library (see <a href="#lua_pcall"><code>lua_pcall</code></a>).
-Whenever an error occurs during
+<p>
-the compilation or execution of a Lua chunk,
+Luan code can explicitly generate an error by calling the
-control returns to the host,
-which can take appropriate measures
-(such as printing an error message).
-<p>
-Lua code can explicitly generate an error by calling the
 <a href="#pdf-error"><code>error</code></a> function.
-If you need to catch errors in Lua,
+Unlike Lua, Luan has <code>try-catch</code> blocks for catching errors.  This means that there is no need for Lua's <code>pcall</code> and <code>xpcall</code> functions.
-you can use <a href="#pdf-pcall"><code>pcall</code></a> or <a href="#pdf-xpcall"><code>xpcall</code></a>
-to call a given function in <em>protected mode</em>.
 <p>
 Whenever there is an error,
 an <em>error object</em> (also called an <em>error message</em>)
 Lua itself only generates errors where the error object is a string,
 but programs may generate errors with
 any value for the error object.
-<p>
-When you use <a href="#pdf-xpcall"><code>xpcall</code></a> or <a href="#lua_pcall"><code>lua_pcall</code></a>,
-you may give a <em>message handler</em>
-to be called in case of errors.
-This function is called with the original error message
-and returns a new error message.
-It is called before the error unwinds the stack,
-so that it can gather more information about the error,
-for instance by inspecting the stack and creating a stack traceback.
-This message handler is still protected by the protected call;
-so, an error inside the message handler
-will call the message handler again.
-If this loop goes on, Lua breaks it and returns an appropriate message.
 <h2>2.4 &ndash; <a name="2.4">Metatables and Metamethods</a></h2>
 <p>
-Every value in Lua can have a <em>metatable</em>.
+Every table in Luan can have a <em>metatable</em>.
-This <em>metatable</em> is an ordinary Lua table
+This <em>metatable</em> is an ordinary Luan table
-that defines the behavior of the original value
+that defines the behavior of the original table
 under certain special operations.
 You can change several aspects of the behavior
-of operations over a value by setting specific fields in its metatable.
+of operations over a table by setting specific fields in its metatable.
-For instance, when a non-numeric value is the operand of an addition,
+For instance, when a table is the operand of an addition,
-Lua checks for a function in the field "<code>__add</code>" of the value's metatable.
+Luan checks for a function in the field "<code>__add</code>" of the table's metatable.
 If it finds one,
-Lua calls this function to perform the addition.
+Luan calls this function to perform the addition.
+<p>
+Inside Luan's implementation, there is a global metatable that applies to all objects.  This metatable is not exposed to Luan users but can be used to change the behavior of objects other than tables.
 <p>
 The keys in a metatable are derived from the <em>event</em> names;
 the corresponding values are called <em>metamethods</em>.
 In the previous example, the event is <code>"add"</code>
 and the metamethod is the function that performs the addition.
 <p>
 You can query the metatable of any value
-using the <a href="#pdf-getmetatable"><code>getmetatable</code></a> function.
+using the <a href="#pdf-getmetatable"><code>get_metatable</code></a> function.
 <p>
 You can replace the metatable of tables
-using the <a href="#pdf-setmetatable"><code>setmetatable</code></a> function.
+using the <a href="#pdf-setmetatable"><code>set_metatable</code></a> function.
-You cannot change the metatable of other types from Lua
-(except by using the debug library);
-you must use the C&nbsp;API for that.
+<p>
+Tables have individual metatables
+(although multiple tables can share their metatables).
-<p>
+By default, a table has no metatable.
-Tables and full userdata have individual metatables
-(although multiple tables and userdata can share their metatables).
-Values of all other types share one single metatable per type;
+<p>
-that is, there is one single metatable for all numbers,
+A metatable controls how a table behaves in arithmetic operations,
-one for all strings, etc.
-By default, a value has no metatable,
-but the string library sets a metatable for the string type (see <a href="#6.4">&sect;6.4</a>).
-<p>
-A metatable controls how an object behaves in arithmetic operations,
 order comparisons, concatenation, length operation, and indexing.
-A metatable also can define a function to be called
+When Luan performs one of these operations over a table,
-when a userdata or a table is garbage collected.
+it checks whether this table has a metatable with the corresponding event.
-When Lua performs one of these operations over a value,
-it checks whether this value has a metatable with the corresponding event.
 If so, the value associated with that key (the metamethod)
-controls how Lua will perform the operation.
+controls how Luan will perform the operation.
 <p>
 Metatables control the operations listed next.
 Each operation is identified by its corresponding name.
 for instance, the key for operation "add" is the
 string "<code>__add</code>".
 <p>
-The semantics of these operations is better explained by a Lua function
+The semantics of these operations is better explained by a Luan function
 describing how the interpreter executes the operation.
 The code shown here in Lua is only illustrative;
 the real behavior is hard coded in the interpreter
 and it is much more efficient than this simulation.
 All functions used in these descriptions
-(<a href="#pdf-rawget"><code>rawget</code></a>, <a href="#pdf-tonumber"><code>tonumber</code></a>, etc.)
+(<a href="#pdf-rawget"><code>raw_get</code></a>, <a href="#pdf-tonumber"><code>to_number</code></a>, etc.)
 are described in <a href="#6.1">&sect;6.1</a>.
 In particular, to retrieve the metamethod of a given object,
 we use the expression
 <pre>
 metatable(obj)[event]
 </pre><p>
 This should be read as
 <pre>
-rawget(getmetatable(obj) or {}, event)
+raw_get(get_metatable(obj) or {}, event)
 </pre><p>
 This means that the access to a metamethod does not invoke other metamethods,
-and access to objects with no metatables does not fail
+and access to tables with no metatables does not fail
 (it simply results in <b>nil</b>).
+<p>
-<p>
-For the unary <code>-</code> and <code>#</code> operators,
-the metamethod is called with a dummy second argument.
-This extra argument is only to simplify Lua's internals;
-it may be removed in future versions and therefore it is not present
-in the following code.
-(For most uses this extra argument is irrelevant.)
 <ul>
 <li><b>"add": </b>
 the <code>+</code> operation.
 <p>
-The function <code>getbinhandler</code> below defines how Lua chooses a handler
+The function <code>get_bin_handler</code> below defines how Luan chooses a handler
 for a binary operation.
-First, Lua tries the first operand.
+First, Luan tries the first operand.
 If its type does not define a handler for the operation,
 then Lua tries the second operand.
 <pre>
-function getbinhandler (op1, op2, event)
+function get_bin_handler (op1, op2, event)
 return metatable(op1)[event] or metatable(op2)[event]
 end
 </pre><p>
 By using this function,
 the behavior of the <code>op1 + op2</code> is
 <pre>
 function add_event (op1, op2)
-local o1, o2 = tonumber(op1), tonumber(op2)
+local o1, o2 = to_number(op1), to_number(op2)
 if o1 and o2 then  -- both operands are numeric?
 return o1 + o2   -- '+' here is the primitive 'add'
 else  -- at least one of the operands is not numeric
-local h = getbinhandler(op1, op2, "__add")
+local h = get_bin_handler(op1, op2, "__add")
 if h then
 -- call the handler with both operands
 return (h(op1, op2))
 else  -- no handler available: default behavior
 error(&middot;&middot;&middot;)
 the <code>*</code> operation.
 Behavior similar to the "add" operation.
 </li>
-<li><b>"div": </b>
+<li><b>"span": </b>
 the <code>/</code> operation.
 Behavior similar to the "add" operation.
 </li>
 the unary <code>-</code> operation.
 <pre>
 function unm_event (op)
-local o = tonumber(op)
+local o = to_number(op)
 if o then  -- operand is numeric?
 return -o  -- '-' here is the primitive 'unm'
 else  -- the operand is not numeric.
 -- Try to get a handler from the operand
 local h = metatable(op).__unm
 function concat_event (op1, op2)
 if (type(op1) == "string" or type(op1) == "number") and
 (type(op2) == "string" or type(op2) == "number") then
 return op1 .. op2  -- primitive string concatenation
 else
-local h = getbinhandler(op1, op2, "__concat")
+local h = get_bin_handler(op1, op2, "__concat")
 if h then
 return (h(op1, op2))
 else
 error(&middot;&middot;&middot;)
 end
 </li>
 <li><b>"eq": </b>
 the <code>==</code> operation.
-The function <code>getequalhandler</code> defines how Lua chooses a metamethod
+The function <code>get_equal_handler</code> defines how Luan chooses a metamethod
 for equality.
 A metamethod is selected only when both values
 being compared have the same type
 and the same metamethod for the selected operation,
 and the values are either tables or full userdata.
 <pre>
-function getequalhandler (op1, op2)
+function get_equal_handler (op1, op2)
 if type(op1) ~= type(op2) or
 (type(op1) ~= "table" and type(op1) ~= "userdata") then
 return nil     -- different values
 end
 local mm1 = metatable(op1).__eq
 function eq_event (op1, op2)
 if op1 == op2 then   -- primitive equal?
 return true   -- values are equal
 end
 -- try metamethod
-local h = getequalhandler(op1, op2)
+local h = get_equal_handler(op1, op2)
 if h then
-return not not h(op1, op2)
+return to_boolean(h(op1, op2))
 else
 return false
 end
 end
 </pre><p>
 if type(op1) == "number" and type(op2) == "number" then
 return op1 &lt; op2   -- numeric comparison
 elseif type(op1) == "string" and type(op2) == "string" then
 return op1 &lt; op2   -- lexicographic comparison
 else
-local h = getbinhandler(op1, op2, "__lt")
+local h = get_bin_handler(op1, op2, "__lt")
 if h then
-return not not h(op1, op2)
+return to_boolean(h(op1, op2))
 else
 error(&middot;&middot;&middot;)
 end
 end
 end
 if type(op1) == "number" and type(op2) == "number" then
 return op1 &lt;= op2   -- numeric comparison
 elseif type(op1) == "string" and type(op2) == "string" then
 return op1 &lt;= op2   -- lexicographic comparison
 else
-local h = getbinhandler(op1, op2, "__le")
+local h = get_bin_handler(op1, op2, "__le")
 if h then
-return not not h(op1, op2)
+return to_boolean(h(op1, op2))
 else
-h = getbinhandler(op1, op2, "__lt")
+h = get_bin_handler(op1, op2, "__lt")
 if h then
-return not h(op2, op1)
+return not to_boolean(h(op2, op1))
 else
 error(&middot;&middot;&middot;)
 end
 end
 end
 end
 </pre><p>
 Note that, in the absence of a "le" metamethod,
-Lua tries the "lt", assuming that <code>a &lt;= b</code> is
+Luan tries the "lt", assuming that <code>a &lt;= b</code> is
 equivalent to <code>not (b &lt; a)</code>.
 <p>
 As with the other comparison operators,
 no key is ever present,
 so the metamethod is always tried.)
 <pre>
-function gettable_event (table, key)
+function get_table_event (table, key)
 local h
 if type(table) == "table" then
-local v = rawget(table, key)
+local v = raw_get(table, key)
 -- if key is present, return raw value
 if v ~= nil then return v end
 h = metatable(table).__index
 if h == nil then return nil end
 else
 Note that the metamethod is tried only
 when <code>key</code> is not present in <code>table</code>.
 <pre>
-function settable_event (table, key, value)
+function set_table_event (table, key, value)
 local h
 if type(table) == "table" then
-local v = rawget(table, key)
+local v = raw_get(table, key)
 -- if key is present, do raw assignment
-if v ~= nil then rawset(table, key, value); return end
+if v ~= nil then raw_set(table, key, value); return end
 h = metatable(table).__newindex
-if h == nil then rawset(table, key, value); return end
+if h == nil then raw_set(table, key, value); return end
 else
 h = metatable(table).__newindex
 if h == nil then
 error(&middot;&middot;&middot;)
 end
 end
 </pre><p>
 </li>
 <li><b>"call": </b>
-called when Lua calls a value.
+called when Luan calls a value.
 <pre>
 function function_event (func, ...)
 if type(func) == "function" then
 <h2>2.5 &ndash; <a name="2.5">Garbage Collection</a></h2>
 <p>
-Lua performs automatic memory management.
+Luan uses Java's garbage collection, so there is very little to say on this subject.  So this section is just a place holder to replace the long explanation of Lua's garbage collection which isn't needed by Luan.
-This means that
-you have to worry neither about allocating memory for new objects
+<p>
-nor about freeing it when the objects are no longer needed.
+Lua has <em>weak tables</em> which is a good concept but is not yet implemented in Luan.  It will be added when there is a need.
-Lua manages memory automatically by running
-a <em>garbage collector</em> to collect all <em>dead objects</em>
-(that is, objects that are no longer accessible from Lua).
-All memory used by Lua is subject to automatic management:
-strings, tables, userdata, functions, threads, internal structures, etc.
-<p>
-Lua implements an incremental mark-and-sweep collector.
-It uses two numbers to control its garbage-collection cycles:
-the <em>garbage-collector pause</em> and
-the <em>garbage-collector step multiplier</em>.
-Both use percentage points as units
-(e.g., a value of 100 means an internal value of 1).
-<p>
-The garbage-collector pause
-controls how long the collector waits before starting a new cycle.
-Larger values make the collector less aggressive.
-Values smaller than 100 mean the collector will not wait to
-start a new cycle.
-A value of 200 means that the collector waits for the total memory in use
-to double before starting a new cycle.
-<p>
-The garbage-collector step multiplier
-controls the relative speed of the collector relative to
-memory allocation.
-Larger values make the collector more aggressive but also increase
-the size of each incremental step.
-Values smaller than 100 make the collector too slow and
-can result in the collector never finishing a cycle.
-The default is 200,
-which means that the collector runs at "twice"
-the speed of memory allocation.
-<p>
-If you set the step multiplier to a very large number
-(larger than 10% of the maximum number of
-bytes that the program may use),
-the collector behaves like a stop-the-world collector.
-If you then set the pause to 200,
-the collector behaves as in old Lua versions,
-doing a complete collection every time Lua doubles its
-memory usage.
-<p>
-You can change these numbers by calling <a href="#lua_gc"><code>lua_gc</code></a> in C
-or <a href="#pdf-collectgarbage"><code>collectgarbage</code></a> in Lua.
-You can also use these functions to control
-the collector directly (e.g., stop and restart it).
-<p>
-As an experimental feature in Lua 5.2,
-you can change the collector's operation mode
-from incremental to <em>generational</em>.
-A <em>generational collector</em> assumes that most objects die young,
-and therefore it traverses only young (recently created) objects.
-This behavior can reduce the time used by the collector,
-but also increases memory usage (as old dead objects may accumulate).
-To mitigate this second problem,
-from time to time the generational collector performs a full collection.
-Remember that this is an experimental feature;
-you are welcome to try it,
-but check your gains.
-<h3>2.5.1 &ndash; <a name="2.5.1">Garbage-Collection Metamethods</a></h3>
-<p>
-You can set garbage-collector metamethods for tables
-and, using the C&nbsp;API,
-for full userdata (see <a href="#2.4">&sect;2.4</a>).
-These metamethods are also called <em>finalizers</em>.
-Finalizers allow you to coordinate Lua's garbage collection
-with external resource management
-(such as closing files, network or database connections,
-or freeing your own memory).
-<p>
-For an object (table or userdata) to be finalized when collected,
-you must <em>mark</em> it for finalization.
-You mark an object for finalization when you set its metatable
-and the metatable has a field indexed by the string "<code>__gc</code>".
-Note that if you set a metatable without a <code>__gc</code> field
-and later create that field in the metatable,
-the object will not be marked for finalization.
-However, after an object is marked,
-you can freely change the <code>__gc</code> field of its metatable.
-<p>
-When a marked object becomes garbage,
-it is not collected immediately by the garbage collector.
-Instead, Lua puts it in a list.
-After the collection,
-Lua does the equivalent of the following function
-for each object in that list:
-<pre>
-function gc_event (obj)
-local h = metatable(obj).__gc
-if type(h) == "function" then
-h(obj)
-end
-end
-</pre>
-<p>
-At the end of each garbage-collection cycle,
-the finalizers for objects are called in
-the reverse order that they were marked for collection,
-among those collected in that cycle;
-that is, the first finalizer to be called is the one associated
-with the object marked last in the program.
-The execution of each finalizer may occur at any point during
-the execution of the regular code.
-<p>
-Because the object being collected must still be used by the finalizer,
-it (and other objects accessible only through it)
-must be <em>resurrected</em> by Lua.
-Usually, this resurrection is transient,
-and the object memory is freed in the next garbage-collection cycle.
-However, if the finalizer stores the object in some global place
-(e.g., a global variable),
-then there is a permanent resurrection.
-In any case,
-the object memory is freed only when it becomes completely inaccessible;
-its finalizer will never be called twice.
-<p>
-When you close a state (see <a href="#lua_close"><code>lua_close</code></a>),
-Lua calls the finalizers of all objects marked for finalization,
-following the reverse order that they were marked.
-If any finalizer marks new objects for collection during that phase,
-these new objects will not be finalized.
-<h3>2.5.2 &ndash; <a name="2.5.2">Weak Tables</a></h3>
-<p>
-A <em>weak table</em> is a table whose elements are
-<em>weak references</em>.
-A weak reference is ignored by the garbage collector.
-In other words,
-if the only references to an object are weak references,
-then the garbage collector will collect that object.
-<p>
-A weak table can have weak keys, weak values, or both.
-A table with weak keys allows the collection of its keys,
-but prevents the collection of its values.
-A table with both weak keys and weak values allows the collection of
-both keys and values.
-In any case, if either the key or the value is collected,
-the whole pair is removed from the table.
-The weakness of a table is controlled by the
-<code>__mode</code> field of its metatable.
-If the <code>__mode</code> field is a string containing the character&nbsp;'<code>k</code>',
-the keys in the table are weak.
-If <code>__mode</code> contains '<code>v</code>',
-the values in the table are weak.
-<p>
-A table with weak keys and strong values
-is also called an <em>ephemeron table</em>.
-In an ephemeron table,
-a value is considered reachable only if its key is reachable.
-In particular,
-if the only reference to a key comes through its value,
-the pair is removed.
-<p>
-Any change in the weakness of a table may take effect only
-at the next collect cycle.
-In particular, if you change the weakness to a stronger mode,
-Lua may still collect some items from that table
-before the change takes effect.
-<p>
-Only objects that have an explicit construction
-are removed from weak tables.
-Values, such as numbers and light C functions,
-are not subject to garbage collection,
-and therefore are not removed from weak tables
-(unless its associated value is collected).
-Although strings are subject to garbage collection,
-they do not have an explicit construction,
-and therefore are not removed from weak tables.
-<p>
-Resurrected objects
-(that is, objects being finalized
-and objects accessible only through objects being finalized)
-have a special behavior in weak tables.
-They are removed from weak values before running their finalizers,
-but are removed from weak keys only in the next collection
-after running their finalizers, when such objects are actually freed.
-This behavior allows the finalizer to access properties
-associated with the object through weak tables.
-<p>
-If a weak table is among the resurrected objects in a collection cycle,
-it may not be properly cleared until the next cycle.
 <h2>2.6 &ndash; <a name="2.6">Coroutines</a></h2>
 <p>
-Lua supports coroutines,
+Unlike Lua, Luan does not support coroutines.  Yes coroutines are cool, but they are not simple, so in the name of simplicity, Luan does without them.
-also called <em>collaborative multithreading</em>.
-A coroutine in Lua represents an independent thread of execution.
-Unlike threads in multithread systems, however,
-a coroutine only suspends its execution by explicitly calling
-a yield function.
-<p>
-You create a coroutine by calling <a href="#pdf-coroutine.create"><code>coroutine.create</code></a>.
-Its sole argument is a function
-that is the main function of the coroutine.
-The <code>create</code> function only creates a new coroutine and
-returns a handle to it (an object of type <em>thread</em>);
-it does not start the coroutine.
-<p>
-You execute a coroutine by calling <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>.
-When you first call <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>,
-passing as its first argument
-a thread returned by <a href="#pdf-coroutine.create"><code>coroutine.create</code></a>,
-the coroutine starts its execution,
-at the first line of its main function.
-Extra arguments passed to <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a> are passed on
-to the coroutine main function.
-After the coroutine starts running,
-it runs until it terminates or <em>yields</em>.
-<p>
-A coroutine can terminate its execution in two ways:
-normally, when its main function returns
-(explicitly or implicitly, after the last instruction);
-and abnormally, if there is an unprotected error.
-In the first case, <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a> returns <b>true</b>,
-plus any values returned by the coroutine main function.
-In case of errors, <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a> returns <b>false</b>
-plus an error message.
-<p>
-A coroutine yields by calling <a href="#pdf-coroutine.yield"><code>coroutine.yield</code></a>.
-When a coroutine yields,
-the corresponding <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a> returns immediately,
-even if the yield happens inside nested function calls
-(that is, not in the main function,
-but in a function directly or indirectly called by the main function).
-In the case of a yield, <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a> also returns <b>true</b>,
-plus any values passed to <a href="#pdf-coroutine.yield"><code>coroutine.yield</code></a>.
-The next time you resume the same coroutine,
-it continues its execution from the point where it yielded,
-with the call to <a href="#pdf-coroutine.yield"><code>coroutine.yield</code></a> returning any extra
-arguments passed to <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>.
-<p>
-Like <a href="#pdf-coroutine.create"><code>coroutine.create</code></a>,
-the <a href="#pdf-coroutine.wrap"><code>coroutine.wrap</code></a> function also creates a coroutine,
-but instead of returning the coroutine itself,
-it returns a function that, when called, resumes the coroutine.
-Any arguments passed to this function
-go as extra arguments to <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>.
-<a href="#pdf-coroutine.wrap"><code>coroutine.wrap</code></a> returns all the values returned by <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>,
-except the first one (the boolean error code).
-Unlike <a href="#pdf-coroutine.resume"><code>coroutine.resume</code></a>,
-<a href="#pdf-coroutine.wrap"><code>coroutine.wrap</code></a> does not catch errors;
-any error is propagated to the caller.
-<p>
-As an example of how coroutines work,
-consider the following code:
-<pre>
-function foo (a)
-print("foo", a)
-return coroutine.yield(2*a)
-end
-co = coroutine.create(function (a,b)
-print("co-body", a, b)
-local r = foo(a+1)
-print("co-body", r)
-local r, s = coroutine.yield(a+b, a-b)
-print("co-body", r, s)
-return b, "end"
-end)
-print("main", coroutine.resume(co, 1, 10))
-print("main", coroutine.resume(co, "r"))
-print("main", coroutine.resume(co, "x", "y"))
-print("main", coroutine.resume(co, "x", "y"))
-</pre><p>
-When you run it, it produces the following output:
-<pre>
-co-body 1       10
-foo     2
-main    true    4
-co-body r
-main    true    11      -9
-co-body x       y
-main    true    10      end
-main    false   cannot resume dead coroutine
-</pre>
-<p>
-You can also create and manipulate coroutines through the C API:
-see functions <a href="#lua_newthread"><code>lua_newthread</code></a>, <a href="#lua_resume"><code>lua_resume</code></a>,
-and <a href="#lua_yield"><code>lua_yield</code></a>.
 <h1>3 &ndash; <a name="3">The Language</a></h1>
 <p>
-This section describes the lexis, the syntax, and the semantics of Lua.
+This section describes the lexis, the syntax, and the semantics of Luan.
 In other words,
 this section describes
 which tokens are valid,
 how they can be combined,
 and what their combinations mean.
 {<em>a</em>}&nbsp;means&nbsp;0 or more <em>a</em>'s, and
 [<em>a</em>]&nbsp;means an optional <em>a</em>.
 Non-terminals are shown like non-terminal,
 keywords are shown like <b>kword</b>,
 and other terminal symbols are shown like &lsquo;<b>=</b>&rsquo;.
-The complete syntax of Lua can be found in <a href="#9">&sect;9</a>
+The complete syntax of Luan can be found in <a href="#9">&sect;9</a>
 at the end of this manual.
 <h2>3.1 &ndash; <a name="3.1">Lexical Conventions</a></h2>
 <p>
-Lua is a free-form language.
+Luan ignores spaces and comments
-It ignores spaces (including new lines) and comments
 between lexical elements (tokens),
 except as delimiters between names and keywords.
+But unlike Lua, Luan generally treats the newline character as a statement separator.  This is how most languages work.  If a newline is preceded by a backslash, then it is treated like a space.  Also, inside of parenthesis (...), brackets [...], and braces {...}, a newline is treated like a space.  This allows the Luan parser to catch mistakes more easily.
+<p>
+In interactive mode, Luan allows an expression on a line which is then evaluated and printed.  This means that entering <em>1+1</em> on an interactive line will produce <em>2</em>.
 <p>
 <em>Names</em>
 (also called <em>identifiers</em>)
 false     for       function  goto      if        in
 local     nil       not       or        repeat    return
 then      true      until     while
 </pre>
+The following <em>keywords</em> are also reserved in Luan but not in Lua:
+<pre>
+catch     import    try
+</pre>
 <p>
 Lua is a case-sensitive language:
 <code>and</code> is a reserved word, but <code>And</code> and <code>AND</code>
 are two different, valid names.
 As a convention, names starting with an underscore followed by
 The following strings denote other tokens:
 <pre>
 +     -     *     /     %     ^     #
 ==    ~=    &lt;=    &gt;=    &lt;     &gt;     =
-(     )     {     }     [     ]     ::
+(     )     {     }     [     ]
 ;     :     ,     .     ..    ...
 </pre>
 <p>
 <em>Literal strings</em>
 (carriage return, newline, carriage return followed by newline,
 or newline followed by carriage return)
 is converted to a simple newline.
-<p>
-Any byte in a literal string not
-explicitly affected by the previous rules represents itself.
-However, Lua opens files for parsing in text mode,
-and the system file functions may have problems with
-some control characters.
-So, it is safer to represent
-non-text data as a quoted literal with
-explicit escape sequences for non-text characters.
 <p>
 For convenience,
 when the opening long bracket is immediately followed by a newline,
 the newline is not included in the string.
 <pre>
 	var ::= prefixexp &lsquo;<b>[</b>&rsquo; exp &lsquo;<b>]</b>&rsquo;
 </pre><p>
 The meaning of accesses to table fields can be changed via metatables.
 An access to an indexed variable <code>t[i]</code> is equivalent to
-a call <code>gettable_event(t,i)</code>.
+a call <code>get_table_event(t,i)</code>.
 (See <a href="#2.4">&sect;2.4</a> for a complete description of the
-<code>gettable_event</code> function.
+<code>get_table_event</code> function.
 This function is not defined or callable in Lua.
 We use it here only for explanatory purposes.)
 <p>
 <pre>
 	stat ::= &lsquo;<b>;</b>&rsquo;
 </pre>
-<p>
-Function calls and assignments
-can start with an open parenthesis.
-This possibility leads to an ambiguity in Lua's grammar.
-Consider the following fragment:
-<pre>
-a = b + c
-(print or io.write)('done')
-</pre><p>
-The grammar could see it in two ways:
-<pre>
-a = b + c(print or io.write)('done')
-a = b + c; (print or io.write)('done')
-</pre><p>
-The current parser always sees such constructions
-in the first way,
-interpreting the open parenthesis
-as the start of the arguments to a call.
-To avoid this ambiguity,
-it is a good practice to always precede with a semicolon
-statements that start with a parenthesis:
-<pre>
-;(print or io.write)('done')
-</pre>
 <p>
 A block can be explicitly delimited to produce a single statement:
 <pre>
 	stat ::= <b>do</b> block <b>end</b>
 </pre><p>
 Explicit blocks are useful
 to control the scope of variable declarations.
-Explicit blocks are also sometimes used to
-add a <b>return</b> statement in the middle
-of another block (see <a href="#3.3.4">&sect;3.3.4</a>).
 A chunk can be stored in a file or in a string inside the host program.
 To execute a chunk,
 Lua first precompiles the chunk into instructions for a virtual machine,
 and then it executes the compiled code
 with an interpreter for the virtual machine.
-<p>
-Chunks can also be precompiled into binary form;
-see program <code>luac</code> for details.
-Programs in source and compiled forms are interchangeable;
-Lua automatically detects the file type and acts accordingly.
 <pre>
 	stat ::= <b>while</b> exp <b>do</b> block <b>end</b>
 	stat ::= <b>repeat</b> block <b>until</b> exp
 	stat ::= <b>if</b> exp <b>then</b> block {<b>elseif</b> exp <b>then</b> block} [<b>else</b> block] <b>end</b>
 </pre><p>
-Lua also has a <b>for</b> statement, in two flavors (see <a href="#3.3.5">&sect;3.3.5</a>).
+Lua also has a <b>for</b> statement (see <a href="#3.3.5">&sect;3.3.5</a>).
 <p>
 The condition expression of a
-control structure can return any value.
+control structure must return a boolean.
-Both <b>false</b> and <b>nil</b> are considered false.
+This is unlike Lua and is intended to catch programming errors more quickly.
-All values different from <b>nil</b> and <b>false</b> are considered true
-(in particular, the number 0 and the empty string are also true).
 <p>
 In the <b>repeat</b>&ndash;<b>until</b> loop,
 the inner block does not end at the <b>until</b> keyword,
 but only after the condition.
 So, the condition can refer to local variables
 declared inside the loop block.
-<p>
-The <b>goto</b> statement transfers the program control to a label.
-For syntactical reasons,
-labels in Lua are considered statements too:
-<pre>
-	stat ::= <b>goto</b> Name
-	stat ::= label
-	label ::= &lsquo;<b>::</b>&rsquo; Name &lsquo;<b>::</b>&rsquo;
-</pre>
-<p>
-A label is visible in the entire block where it is defined,
-except
-inside nested blocks where a label with the same name is defined and
-inside nested functions.
-A goto may jump to any visible label as long as it does not
-enter into the scope of a local variable.
-<p>
-Labels and empty statements are called <em>void statements</em>,
-as they perform no actions.
 <p>
 The <b>break</b> statement terminates the execution of a
 <b>while</b>, <b>repeat</b>, or <b>for</b> loop,
 <pre>
 	stat ::= <b>return</b> [explist] [&lsquo;<b>;</b>&rsquo;]
 </pre>
-<p>
-The <b>return</b> statement can only be written
-as the last statement of a block.
-If it is really necessary to <b>return</b> in the middle of a block,
-then an explicit inner block can be used,
-as in the idiom <code>do return end</code>,
-because now <b>return</b> is the last statement in its (inner) block.
 <h3>3.3.5 &ndash; <a name="3.3.5">For Statement</a></h3>
-<p>
+<p>
-The <b>for</b> statement has two forms:
+The <b>for</b> statement works over functions,
-one numeric and one generic.
-<p>
-The numeric <b>for</b> loop repeats a block of code while a
-control variable runs through an arithmetic progression.
-It has the following syntax:
-<pre>
-	stat ::= <b>for</b> Name &lsquo;<b>=</b>&rsquo; exp &lsquo;<b>,</b>&rsquo; exp [&lsquo;<b>,</b>&rsquo; exp] <b>do</b> block <b>end</b>
-</pre><p>
-The <em>block</em> is repeated for <em>name</em> starting at the value of
-the first <em>exp</em>, until it passes the second <em>exp</em> by steps of the
-third <em>exp</em>.
-More precisely, a <b>for</b> statement like
-<pre>
-for v = <em>e1</em>, <em>e2</em>, <em>e3</em> do <em>block</em> end
-</pre><p>
-is equivalent to the code:
-<pre>
-do
-local <em>var</em>, <em>limit</em>, <em>step</em> = tonumber(<em>e1</em>), tonumber(<em>e2</em>), tonumber(<em>e3</em>)
-if not (<em>var</em> and <em>limit</em> and <em>step</em>) then error() end
-while (<em>step</em> &gt; 0 and <em>var</em> &lt;= <em>limit</em>) or (<em>step</em> &lt;= 0 and <em>var</em> &gt;= <em>limit</em>) do
-local v = <em>var</em>
-<em>block</em>
-<em>var</em> = <em>var</em> + <em>step</em>
-end
-end
-</pre><p>
-Note the following:
-<ul>
-<li>
-All three control expressions are evaluated only once,
-before the loop starts.
-They must all result in numbers.
-</li>
-<li>
-<code><em>var</em></code>, <code><em>limit</em></code>, and <code><em>step</em></code> are invisible variables.
-The names shown here are for explanatory purposes only.
-</li>
-<li>
-If the third expression (the step) is absent,
-then a step of&nbsp;1 is used.
-</li>
-<li>
-You can use <b>break</b> to exit a <b>for</b> loop.
-</li>
-<li>
-The loop variable <code>v</code> is local to the loop;
-you cannot use its value after the <b>for</b> ends or is broken.
-If you need this value,
-assign it to another variable before breaking or exiting the loop.
-</li>
-</ul>
-<p>
-The generic <b>for</b> statement works over functions,
 called <em>iterators</em>.
 On each iteration, the iterator function is called to produce a new value,
 stopping when this new value is <b>nil</b>.
-The generic <b>for</b> loop has the following syntax:
+The <b>for</b> loop has the following syntax:
 <pre>
 	stat ::= <b>for</b> namelist <b>in</b> explist <b>do</b> block <b>end</b>
 	namelist ::= Name {&lsquo;<b>,</b>&rsquo; Name}
 </pre><p>
 A <b>for</b> statement like
 <pre>
-for <em>var_1</em>, &middot;&middot;&middot;, <em>var_n</em> in <em>explist</em> do <em>block</em> end
+for <em>var_1</em>, &middot;&middot;&middot;, <em>var_n</em> in <em>expression</em> do <em>block</em> end
 </pre><p>
 is equivalent to the code:
 <pre>
 do
-local <em>f</em>, <em>s</em>, <em>var</em> = <em>explist</em>
+local <em>f</em> = <em>expression</em>
 while true do
-local <em>var_1</em>, &middot;&middot;&middot;, <em>var_n</em> = <em>f</em>(<em>s</em>, <em>var</em>)
+local <em>var_1</em>, &middot;&middot;&middot;, <em>var_n</em> = <em>f</em>()
 if <em>var_1</em> == nil then break end
-<em>var</em> = <em>var_1</em>
 <em>block</em>
 end
 end
 </pre><p>
 Note the following:
 <ul>
 <li>
-<code><em>explist</em></code> is evaluated only once.
+<code><em>expression</em></code> is evaluated only once.
-Its results are an <em>iterator</em> function,
+Its result is an <em>iterator</em> function.
-a <em>state</em>,
-and an initial value for the first <em>iterator variable</em>.
 </li>
 <li>
-<code><em>f</em></code>, <code><em>s</em></code>, and <code><em>var</em></code> are invisible variables.
+<code><em>f</em></code> is an invisible variable.
-The names are here for explanatory purposes only.
+The name is here for explanatory purposes only.
 </li>
 <li>
 You can use <b>break</b> to exit a <b>for</b> loop.
 </li>
 then assign them to other variables before breaking or exiting the loop.
 </li>
 </ul>
+<p>
+Lua also has a numeric <b>for</b> statement which Luan does not support.  Instead, Luan offers the <em>range</em> function (inspired by Python) which does the same thing without adding to the syntax of the language.
 <h3>3.3.6 &ndash; <a name="3.3.6">Function Calls as Statements</a></h3><p>
 To allow possible side-effects,
 function calls can be executed as statements:
 </pre><p>
 If present, an initial assignment has the same semantics
 of a multiple assignment (see <a href="#3.3.3">&sect;3.3.3</a>).
 Otherwise, all variables are initialized with <b>nil</b>.
 <p>
 A chunk is also a block (see <a href="#3.3.2">&sect;3.3.2</a>),
 and so local variables can be declared in a chunk outside any explicit block.
 <p>
 The visibility rules for local variables are explained in <a href="#3.5">&sect;3.5</a>.
+<h3>3.3.8 &ndash; <a name="3.3.8">Or/And Statements</a></h3><p>
+<p>
+An <b>or</b> or <b>and</b> expression is also considered a statement.  This is new for Luan and doesn't exist in Lua.
+<p>For example, consider a function <em>do_something</em> that returns a boolean indicating whether it succeeded or failed.  You can then do:
+<pre>
+	do_something() or error "didn't work"
+</pre>
 <h2>3.4 &ndash; <a name="3.4">Expressions</a></h2>
 <p>
-The basic expressions in Lua are the following:
+The basic expressions in Luan are the following:
 <pre>
 	exp ::= prefixexp
 	exp ::= <b>nil</b> | <b>false</b> | <b>true</b>
 	exp ::= Number
 or <b>nil</b> if <code>f</code> does not return any values.)
 <h3>3.4.1 &ndash; <a name="3.4.1">Arithmetic Operators</a></h3><p>
-Lua supports the usual arithmetic operators:
+Luan supports the usual arithmetic operators:
 the binary <code>+</code> (addition),
 <code>-</code> (subtraction), <code>*</code> (multiplication),
 <code>/</code> (division), <code>%</code> (modulo), and <code>^</code> (exponentiation);
 and unary <code>-</code> (mathematical negation).
 If the operands are numbers, or strings that can be converted to
 Exponentiation works for any exponent.
 For instance, <code>x^(-0.5)</code> computes the inverse of the square root of <code>x</code>.
 Modulo is defined as
 <pre>
-a % b == a - math.floor(a/b)*b
+a % b == a - Math.floor(a/b)*b
 </pre><p>
 That is, it is the remainder of a division that rounds
 the quotient towards minus infinity.
 <h3>3.4.2 &ndash; <a name="3.4.2">Coercion</a></h3>
 <p>
-Lua provides automatic conversion between
+Luan provides automatic conversion between
 string and number values at run time.
 Any arithmetic operation applied to a string tries to convert
 this string to a number, following the rules of the Lua lexer.
 (The string may have leading and trailing spaces and a sign.)
 Conversely, whenever a number is used where a string is expected,
 <h3>3.4.3 &ndash; <a name="3.4.3">Relational Operators</a></h3><p>
-The relational operators in Lua are
+The relational operators in Luan are
 <pre>
 ==    ~=    &lt;     &gt;     &lt;=    &gt;=
 </pre><p>
 These operators always result in <b>false</b> or <b>true</b>.
 Closures with any detectable difference
 (different behavior, different definition) are always different.
 <p>
-You can change the way that Lua compares tables and userdata
+You can change the way that Luan compares tables
 by using the "eq" metamethod (see <a href="#2.4">&sect;2.4</a>).
 <p>
 The conversion rules of <a href="#3.4.2">&sect;3.4.2</a>
 <h3>3.4.5 &ndash; <a name="3.4.5">Concatenation</a></h3><p>
-The string concatenation operator in Lua is
+The string concatenation operator in Luan is
 denoted by two dots ('<code>..</code>').
 If both operands are strings or numbers, then they are converted to
 strings according to the rules mentioned in <a href="#3.4.2">&sect;3.4.2</a>.
 Otherwise, the <code>__concat</code> metamethod is called (see <a href="#2.4">&sect;2.4</a>).
 <h3>3.4.7 &ndash; <a name="3.4.7">Precedence</a></h3><p>
-Operator precedence in Lua follows the table below,
+Operator precedence in Luan follows the table below,
 from lower to higher priority:
 <pre>
 or
 and
 <h3>3.4.9 &ndash; <a name="3.4.9">Function Calls</a></h3><p>
-A function call in Lua has the following syntax:
+A function call in Luan has the following syntax:
 <pre>
 	functioncall ::= prefixexp args
 </pre><p>
 In a function call,
 followed by the original call arguments
 (see <a href="#2.4">&sect;2.4</a>).
 <p>
-The form
+Lua supports a special function call for "methods" like <em>obj:fn(args)</em> .  Luan does not support this.
-<pre>
-	functioncall ::= prefixexp &lsquo;<b>:</b>&rsquo; Name args
-</pre><p>
-can be used to call "methods".
-A call <code>v:name(<em>args</em>)</code>
-is syntactic sugar for <code>v.name(v,<em>args</em>)</code>,
-except that <code>v</code> is evaluated only once.
 <p>
 Arguments have the following syntax:
 <pre>
 <p>
 A call of the form <code>return <em>functioncall</em></code> is called
 a <em>tail call</em>.
-Lua implements <em>proper tail calls</em>
+Luan implements <em>proper tail calls</em>
 (or <em>proper tail recursion</em>):
 in a tail call,
 the called function reuses the stack entry of the calling function.
 Therefore, there is no limit on the number of nested tail calls that
 a program can execute.
 The following syntactic sugar simplifies function definitions:
 <pre>
 	stat ::= <b>function</b> funcname funcbody
 	stat ::= <b>local</b> <b>function</b> Name funcbody
-	funcname ::= Name {&lsquo;<b>.</b>&rsquo; Name} [&lsquo;<b>:</b>&rsquo; Name]
+	funcname ::= Name {&lsquo;<b>.</b>&rsquo; Name}
 </pre><p>
 The statement
 <pre>
 function f () <em>body</em> end
 <p>
 A function definition is an executable expression,
 whose value has type <em>function</em>.
-When Lua precompiles a chunk,
+When Luan precompiles a chunk,
 all its function bodies are precompiled too.
-Then, whenever Lua executes the function definition,
+Then, whenever Luan executes the function definition,
 the function is <em>instantiated</em> (or <em>closed</em>).
 This function instance (or <em>closure</em>)
 is the final value of the expression.
 If control reaches the end of a function
 without encountering a <b>return</b> statement,
 then the function returns with no results.
-<p>
-There is a system-dependent limit on the number of values
-that a function may return.
-This limit is guaranteed to be larger than 1000.
-<p>
-The <em>colon</em> syntax
-is used for defining <em>methods</em>,
-that is, functions that have an implicit extra parameter <code>self</code>.
-Thus, the statement
-<pre>
-function t.a.b.c:f (<em>params</em>) <em>body</em> end
-</pre><p>
-is syntactic sugar for
-<pre>
-t.a.b.c.f = function (self, <em>params</em>) <em>body</em> end
-</pre>
 <h2>3.5 &ndash; <a name="3.5">Visibility Rules</a></h2>
 <p>
-Lua is a lexically scoped language.
+Luan is a lexically scoped language.
 The scope of a local variable begins at the first statement after
 its declaration and lasts until the last non-void statement
 of the innermost block that includes the declaration.
 Consider the following example:
 <h1>4 &ndash; <a name="4">The Application Program Interface</a></h1>
 <p>
+In the Lua documentation,
-This section describes the C&nbsp;API for Lua, that is,
+this section described the C&nbsp;API for Lua.
-the set of C&nbsp;functions available to the host program to communicate
+Obviously this is not relevant for Luan.
-with Lua.
+The implementation of Luan is radically different from Lua and will be documented eventually in Javadoc.
-All API functions and related types and constants
+So this section is just a placeholder so that Luan documentation can match Lua's documentation.
-are declared in the header file <a name="pdf-lua.h"><code>lua.h</code></a>.
-<p>
-Even when we use the term "function",
-any facility in the API may be provided as a macro instead.
-Except where stated otherwise,
-all such macros use each of their arguments exactly once
-(except for the first argument, which is always a Lua state),
-and so do not generate any hidden side-effects.
-<p>
-As in most C&nbsp;libraries,
-the Lua API functions do not check their arguments for validity or consistency.
-However, you can change this behavior by compiling Lua
-with the macro <a name="pdf-LUA_USE_APICHECK"><code>LUA_USE_APICHECK</code></a> defined.
-<h2>4.1 &ndash; <a name="4.1">The Stack</a></h2>
-<p>
-Lua uses a <em>virtual stack</em> to pass values to and from C.
-Each element in this stack represents a Lua value
-(<b>nil</b>, number, string, etc.).
-<p>
-Whenever Lua calls C, the called function gets a new stack,
-which is independent of previous stacks and of stacks of
-C&nbsp;functions that are still active.
-This stack initially contains any arguments to the C&nbsp;function
-and it is where the C&nbsp;function pushes its results
-to be returned to the caller (see <a href="#lua_CFunction"><code>lua_CFunction</code></a>).
-<p>
-For convenience,
-most query operations in the API do not follow a strict stack discipline.
-Instead, they can refer to any element in the stack
-by using an <em>index</em>:
-A positive index represents an absolute stack position
-(starting at&nbsp;1);
-a negative index represents an offset relative to the top of the stack.
-More specifically, if the stack has <em>n</em> elements,
-then index&nbsp;1 represents the first element
-(that is, the element that was pushed onto the stack first)
-and
-index&nbsp;<em>n</em> represents the last element;
-index&nbsp;-1 also represents the last element
-(that is, the element at the&nbsp;top)
-and index <em>-n</em> represents the first element.
-<h2>4.2 &ndash; <a name="4.2">Stack Size</a></h2>
-<p>
-When you interact with the Lua API,
-you are responsible for ensuring consistency.
-In particular,
-<em>you are responsible for controlling stack overflow</em>.
-You can use the function <a href="#lua_checkstack"><code>lua_checkstack</code></a>
-to ensure that the stack has extra slots when pushing new elements.
-<p>
-Whenever Lua calls C,
-it ensures that the stack has at least <a name="pdf-LUA_MINSTACK"><code>LUA_MINSTACK</code></a> extra slots.
-<code>LUA_MINSTACK</code> is defined as 20,
-so that usually you do not have to worry about stack space
-unless your code has loops pushing elements onto the stack.
-<p>
-When you call a Lua function
-without a fixed number of results (see <a href="#lua_call"><code>lua_call</code></a>),
-Lua ensures that the stack has enough size for all results,
-but it does not ensure any extra space.
-So, before pushing anything in the stack after such a call
-you should use <a href="#lua_checkstack"><code>lua_checkstack</code></a>.
-<h2>4.3 &ndash; <a name="4.3">Valid and Acceptable Indices</a></h2>
-<p>
-Any function in the API that receives stack indices
-works only with <em>valid indices</em> or <em>acceptable indices</em>.
-<p>
-A <em>valid index</em> is an index that refers to a
-real position within the stack, that is,
-its position lies between&nbsp;1 and the stack top
-(<code>1 &le; abs(index) &le; top</code>).
-Usually, functions that can modify the value at an index
-require valid indices.
-<p>
-Unless otherwise noted,
-any function that accepts valid indices also accepts <em>pseudo-indices</em>,
-which represent some Lua values that are accessible to C&nbsp;code
-but which are not in the stack.
-Pseudo-indices are used to access the registry
-and the upvalues of a C&nbsp;function (see <a href="#4.4">&sect;4.4</a>).
-<p>
-Functions that do not need a specific stack position,
-but only a value in the stack (e.g., query functions),
-can be called with acceptable indices.
-An <em>acceptable index</em> can be any valid index,
-including the pseudo-indices,
-but it also can be any positive index after the stack top
-within the space allocated for the stack,
-that is, indices up to the stack size.
-(Note that 0 is never an acceptable index.)
-Except when noted otherwise,
-functions in the API work with acceptable indices.
-<p>
-Acceptable indices serve to avoid extra tests
-against the stack top when querying the stack.
-For instance, a C&nbsp;function can query its third argument
-without the need to first check whether there is a third argument,
-that is, without the need to check whether 3 is a valid index.
-<p>
-For functions that can be called with acceptable indices,
-any non-valid index is treated as if it
-contains a value of a virtual type <a name="pdf-LUA_TNONE"><code>LUA_TNONE</code></a>,
-which behaves like a nil value.
-<h2>4.4 &ndash; <a name="4.4">C Closures</a></h2>
-<p>
-When a C&nbsp;function is created,
-it is possible to associate some values with it,
-thus creating a <em>C&nbsp;closure</em>
-(see <a href="#lua_pushcclosure"><code>lua_pushcclosure</code></a>);
-these values are called <em>upvalues</em> and are
-accessible to the function whenever it is called.
-<p>
-Whenever a C&nbsp;function is called,
-its upvalues are located at specific pseudo-indices.
-These pseudo-indices are produced by the macro
-<a href="#lua_upvalueindex"><code>lua_upvalueindex</code></a>.
-The first value associated with a function is at position
-<code>lua_upvalueindex(1)</code>, and so on.
-Any access to <code>lua_upvalueindex(<em>n</em>)</code>,
-where <em>n</em> is greater than the number of upvalues of the
-current function (but not greater than 256),
-produces an acceptable but invalid index.
-<h2>4.5 &ndash; <a name="4.5">Registry</a></h2>
-<p>
-Lua provides a <em>registry</em>,
-a predefined table that can be used by any C&nbsp;code to
-store whatever Lua values it needs to store.
-The registry table is always located at pseudo-index
-<a name="pdf-LUA_REGISTRYINDEX"><code>LUA_REGISTRYINDEX</code></a>,
-which is a valid index.
-Any C&nbsp;library can store data into this table,
-but it should take care to choose keys
-that are different from those used
-by other libraries, to avoid collisions.
-Typically, you should use as key a string containing your library name,
-or a light userdata with the address of a C&nbsp;object in your code,
-or any Lua object created by your code.
-As with global names,
-string keys starting with an underscore followed by
-uppercase letters are reserved for Lua.
-<p>
-The integer keys in the registry are used by the reference mechanism,
-implemented by the auxiliary library,
-and by some predefined values.
-Therefore, integer keys should not be used for other purposes.
-<p>
-When you create a new Lua state,
-its registry comes with some predefined values.
-These predefined values are indexed with integer keys
-defined as constants in <code>lua.h</code>.
-The following constants are defined:
-<ul>
-<li><b><a name="pdf-LUA_RIDX_MAINTHREAD"><code>LUA_RIDX_MAINTHREAD</code></a>: </b> At this index the registry has
-the main thread of the state.
-(The main thread is the one created together with the state.)
-</li>
-<li><b><a name="pdf-LUA_RIDX_GLOBALS"><code>LUA_RIDX_GLOBALS</code></a>: </b> At this index the registry has
-the global environment.
-</li>
-</ul>
-<h2>4.6 &ndash; <a name="4.6">Error Handling in C</a></h2>
-<p>
-Internally, Lua uses the C <code>longjmp</code> facility to handle errors.
-(You can also choose to use exceptions if you compile Lua as C++;
-search for <code>LUAI_THROW</code> in the source code.)
-When Lua faces any error
-(such as a memory allocation error, type errors, syntax errors,
-and runtime errors)
-it <em>raises</em> an error;
-that is, it does a long jump.
-A <em>protected environment</em> uses <code>setjmp</code>
-to set a recovery point;
-any error jumps to the most recent active recovery point.
-<p>
-If an error happens outside any protected environment,
-Lua calls a <em>panic function</em> (see <a href="#lua_atpanic"><code>lua_atpanic</code></a>)
-and then calls <code>abort</code>,
-thus exiting the host application.
-Your panic function can avoid this exit by
-never returning
-(e.g., doing a long jump to your own recovery point outside Lua).
-<p>
-The panic function runs as if it were a message handler (see <a href="#2.3">&sect;2.3</a>);
-in particular, the error message is at the top of the stack.
-However, there is no guarantees about stack space.
-To push anything on the stack,
-the panic function should first check the available space (see <a href="#4.2">&sect;4.2</a>).
-<p>
-Most functions in the API can throw an error,
-for instance due to a memory allocation error.
-The documentation for each function indicates whether
-it can throw errors.
-<p>
-Inside a C&nbsp;function you can throw an error by calling <a href="#lua_error"><code>lua_error</code></a>.
-<h2>4.7 &ndash; <a name="4.7">Handling Yields in C</a></h2>
-<p>
-Internally, Lua uses the C <code>longjmp</code> facility to yield a coroutine.
-Therefore, if a function <code>foo</code> calls an API function
-and this API function yields
-(directly or indirectly by calling another function that yields),
-Lua cannot return to <code>foo</code> any more,
-because the <code>longjmp</code> removes its frame from the C stack.
-<p>
-To avoid this kind of problem,
-Lua raises an error whenever it tries to yield across an API call,
-except for three functions:
-<a href="#lua_yieldk"><code>lua_yieldk</code></a>, <a href="#lua_callk"><code>lua_callk</code></a>, and <a href="#lua_pcallk"><code>lua_pcallk</code></a>.
-All those functions receive a <em>continuation function</em>
-(as a parameter called <code>k</code>) to continue execution after a yield.
-<p>
-We need to set some terminology to explain continuations.
-We have a C function called from Lua which we will call
-the <em>original function</em>.
-This original function then calls one of those three functions in the C API,
-which we will call the <em>callee function</em>,
-that then yields the current thread.
-(This can happen when the callee function is <a href="#lua_yieldk"><code>lua_yieldk</code></a>,
-or when the callee function is either <a href="#lua_callk"><code>lua_callk</code></a> or <a href="#lua_pcallk"><code>lua_pcallk</code></a>
-and the function called by them yields.)
-<p>
-Suppose the running thread yields while executing the callee function.
-After the thread resumes,
-it eventually will finish running the callee function.
-However,
-the callee function cannot return to the original function,
-because its frame in the C stack was destroyed by the yield.
-Instead, Lua calls a <em>continuation function</em>,
-which was given as an argument to the callee function.
-As the name implies,
-the continuation function should continue the task
-of the original function.
-<p>
-Lua treats the continuation function as if it were the original function.
-The continuation function receives the same Lua stack
-from the original function,
-in the same state it would be if the callee function had returned.
-(For instance,
-after a <a href="#lua_callk"><code>lua_callk</code></a> the function and its arguments are
-removed from the stack and replaced by the results from the call.)
-It also has the same upvalues.
-Whatever it returns is handled by Lua as if it were the return
-of the original function.
-<p>
-The only difference in the Lua state between the original function
-and its continuation is the result of a call to <a href="#lua_getctx"><code>lua_getctx</code></a>.
-<h2>4.8 &ndash; <a name="4.8">Functions and Types</a></h2>
-<p>
-Here we list all functions and types from the C&nbsp;API in
-alphabetical order.
-Each function has an indicator like this:
-<span class="apii">[-o, +p, <em>x</em>]</span>
-<p>
-The first field, <code>o</code>,
-is how many elements the function pops from the stack.
-The second field, <code>p</code>,
-is how many elements the function pushes onto the stack.
-(Any function always pushes its results after popping its arguments.)
-A field in the form <code>x|y</code> means the function can push (or pop)
-<code>x</code> or <code>y</code> elements,
-depending on the situation;
-an interrogation mark '<code>?</code>' means that
-we cannot know how many elements the function pops/pushes
-by looking only at its arguments
-(e.g., they may depend on what is on the stack).
-The third field, <code>x</code>,
-tells whether the function may throw errors:
-'<code>-</code>' means the function never throws any error;
-'<code>e</code>' means the function may throw errors;
-'<code>v</code>' means the function may throw an error on purpose.
-<hr><h3><a name="lua_absindex"><code>lua_absindex</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_absindex (lua_State *L, int idx);</pre>
-<p>
-Converts the acceptable index <code>idx</code> into an absolute index
-(that is, one that does not depend on the stack top).
-<hr><h3><a name="lua_Alloc"><code>lua_Alloc</code></a></h3>
-<pre>typedef void * (*lua_Alloc) (void *ud,
-void *ptr,
-size_t osize,
-size_t nsize);</pre>
-<p>
-The type of the memory-allocation function used by Lua states.
-The allocator function must provide a
-functionality similar to <code>realloc</code>,
-but not exactly the same.
-Its arguments are
-<code>ud</code>, an opaque pointer passed to <a href="#lua_newstate"><code>lua_newstate</code></a>;
-<code>ptr</code>, a pointer to the block being allocated/reallocated/freed;
-<code>osize</code>, the original size of the block or some code about what
-is being allocated;
-<code>nsize</code>, the new size of the block.
-<p>
-When <code>ptr</code> is not <code>NULL</code>,
-<code>osize</code> is the size of the block pointed by <code>ptr</code>,
-that is, the size given when it was allocated or reallocated.
-<p>
-When <code>ptr</code> is <code>NULL</code>,
-<code>osize</code> encodes the kind of object that Lua is allocating.
-<code>osize</code> is any of
-<a href="#pdf-LUA_TSTRING"><code>LUA_TSTRING</code></a>, <a href="#pdf-LUA_TTABLE"><code>LUA_TTABLE</code></a>, <a href="#pdf-LUA_TFUNCTION"><code>LUA_TFUNCTION</code></a>,
-<a href="#pdf-LUA_TUSERDATA"><code>LUA_TUSERDATA</code></a>, or <a href="#pdf-LUA_TTHREAD"><code>LUA_TTHREAD</code></a> when (and only when)
-Lua is creating a new object of that type.
-When <code>osize</code> is some other value,
-Lua is allocating memory for something else.
-<p>
-Lua assumes the following behavior from the allocator function:
-<p>
-When <code>nsize</code> is zero,
-the allocator should behave like <code>free</code>
-and return <code>NULL</code>.
-<p>
-When <code>nsize</code> is not zero,
-the allocator should behave like <code>realloc</code>.
-The allocator returns <code>NULL</code>
-if and only if it cannot fulfill the request.
-Lua assumes that the allocator never fails when
-<code>osize &gt;= nsize</code>.
-<p>
-Here is a simple implementation for the allocator function.
-It is used in the auxiliary library by <a href="#luaL_newstate"><code>luaL_newstate</code></a>.
-<pre>
-static void *l_alloc (void *ud, void *ptr, size_t osize,
-size_t nsize) {
-(void)ud;  (void)osize;  /* not used */
-if (nsize == 0) {
-free(ptr);
-return NULL;
-}
-else
-return realloc(ptr, nsize);
-}
-</pre><p>
-Note that Standard&nbsp;C ensures
-that <code>free(NULL)</code> has no effect and that
-<code>realloc(NULL, size)</code> is equivalent to <code>malloc(size)</code>.
-This code assumes that <code>realloc</code> does not fail when shrinking a block.
-(Although Standard&nbsp;C does not ensure this behavior,
-it seems to be a safe assumption.)
-<hr><h3><a name="lua_arith"><code>lua_arith</code></a></h3><p>
-<span class="apii">[-(2|1), +1, <em>e</em>]</span>
-<pre>void lua_arith (lua_State *L, int op);</pre>
-<p>
-Performs an arithmetic operation over the two values
-(or one, in the case of negation)
-at the top of the stack,
-with the value at the top being the second operand,
-pops these values, and pushes the result of the operation.
-The function follows the semantics of the corresponding Lua operator
-(that is, it may call metamethods).
-<p>
-The value of <code>op</code> must be one of the following constants:
-<ul>
-<li><b><a name="pdf-LUA_OPADD"><code>LUA_OPADD</code></a>: </b> performs addition (<code>+</code>)</li>
-<li><b><a name="pdf-LUA_OPSUB"><code>LUA_OPSUB</code></a>: </b> performs subtraction (<code>-</code>)</li>
-<li><b><a name="pdf-LUA_OPMUL"><code>LUA_OPMUL</code></a>: </b> performs multiplication (<code>*</code>)</li>
-<li><b><a name="pdf-LUA_OPDIV"><code>LUA_OPDIV</code></a>: </b> performs division (<code>/</code>)</li>
-<li><b><a name="pdf-LUA_OPMOD"><code>LUA_OPMOD</code></a>: </b> performs modulo (<code>%</code>)</li>
-<li><b><a name="pdf-LUA_OPPOW"><code>LUA_OPPOW</code></a>: </b> performs exponentiation (<code>^</code>)</li>
-<li><b><a name="pdf-LUA_OPUNM"><code>LUA_OPUNM</code></a>: </b> performs mathematical negation (unary <code>-</code>)</li>
-</ul>
-<hr><h3><a name="lua_atpanic"><code>lua_atpanic</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_CFunction lua_atpanic (lua_State *L, lua_CFunction panicf);</pre>
-<p>
-Sets a new panic function and returns the old one (see <a href="#4.6">&sect;4.6</a>).
-<hr><h3><a name="lua_call"><code>lua_call</code></a></h3><p>
-<span class="apii">[-(nargs+1), +nresults, <em>e</em>]</span>
-<pre>void lua_call (lua_State *L, int nargs, int nresults);</pre>
-<p>
-Calls a function.
-<p>
-To call a function you must use the following protocol:
-first, the function to be called is pushed onto the stack;
-then, the arguments to the function are pushed
-in direct order;
-that is, the first argument is pushed first.
-Finally you call <a href="#lua_call"><code>lua_call</code></a>;
-<code>nargs</code> is the number of arguments that you pushed onto the stack.
-All arguments and the function value are popped from the stack
-when the function is called.
-The function results are pushed onto the stack when the function returns.
-The number of results is adjusted to <code>nresults</code>,
-unless <code>nresults</code> is <a name="pdf-LUA_MULTRET"><code>LUA_MULTRET</code></a>.
-In this case, all results from the function are pushed.
-Lua takes care that the returned values fit into the stack space.
-The function results are pushed onto the stack in direct order
-(the first result is pushed first),
-so that after the call the last result is on the top of the stack.
-<p>
-Any error inside the called function is propagated upwards
-(with a <code>longjmp</code>).
-<p>
-The following example shows how the host program can do the
-equivalent to this Lua code:
-<pre>
-a = f("how", t.x, 14)
-</pre><p>
-Here it is in&nbsp;C:
-<pre>
-lua_getglobal(L, "f");                  /* function to be called */
-lua_pushstring(L, "how");                        /* 1st argument */
-lua_getglobal(L, "t");                    /* table to be indexed */
-lua_getfield(L, -1, "x");        /* push result of t.x (2nd arg) */
-lua_remove(L, -2);                  /* remove 't' from the stack */
-lua_pushinteger(L, 14);                          /* 3rd argument */
-lua_call(L, 3, 1);     /* call 'f' with 3 arguments and 1 result */
-lua_setglobal(L, "a");                         /* set global 'a' */
-</pre><p>
-Note that the code above is "balanced":
-at its end, the stack is back to its original configuration.
-This is considered good programming practice.
-<hr><h3><a name="lua_callk"><code>lua_callk</code></a></h3><p>
-<span class="apii">[-(nargs + 1), +nresults, <em>e</em>]</span>
-<pre>void lua_callk (lua_State *L, int nargs, int nresults, int ctx,
-lua_CFunction k);</pre>
-<p>
-This function behaves exactly like <a href="#lua_call"><code>lua_call</code></a>,
-but allows the called function to yield (see <a href="#4.7">&sect;4.7</a>).
-<hr><h3><a name="lua_CFunction"><code>lua_CFunction</code></a></h3>
-<pre>typedef int (*lua_CFunction) (lua_State *L);</pre>
-<p>
-Type for C&nbsp;functions.
-<p>
-In order to communicate properly with Lua,
-a C&nbsp;function must use the following protocol,
-which defines the way parameters and results are passed:
-a C&nbsp;function receives its arguments from Lua in its stack
-in direct order (the first argument is pushed first).
-So, when the function starts,
-<code>lua_gettop(L)</code> returns the number of arguments received by the function.
-The first argument (if any) is at index 1
-and its last argument is at index <code>lua_gettop(L)</code>.
-To return values to Lua, a C&nbsp;function just pushes them onto the stack,
-in direct order (the first result is pushed first),
-and returns the number of results.
-Any other value in the stack below the results will be properly
-discarded by Lua.
-Like a Lua function, a C&nbsp;function called by Lua can also return
-many results.
-<p>
-As an example, the following function receives a variable number
-of numerical arguments and returns their average and sum:
-<pre>
-static int foo (lua_State *L) {
-int n = lua_gettop(L);    /* number of arguments */
-lua_Number sum = 0;
-int i;
-for (i = 1; i &lt;= n; i++) {
-if (!lua_isnumber(L, i)) {
-lua_pushstring(L, "incorrect argument");
-lua_error(L);
-}
-sum += lua_tonumber(L, i);
-}
-lua_pushnumber(L, sum/n);        /* first result */
-lua_pushnumber(L, sum);         /* second result */
-return 2;                   /* number of results */
-}
-</pre>
-<hr><h3><a name="lua_checkstack"><code>lua_checkstack</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_checkstack (lua_State *L, int extra);</pre>
-<p>
-Ensures that there are at least <code>extra</code> free stack slots in the stack.
-It returns false if it cannot fulfill the request,
-because it would cause the stack to be larger than a fixed maximum size
-(typically at least a few thousand elements) or
-because it cannot allocate memory for the new stack size.
-This function never shrinks the stack;
-if the stack is already larger than the new size,
-it is left unchanged.
-<hr><h3><a name="lua_close"><code>lua_close</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void lua_close (lua_State *L);</pre>
-<p>
-Destroys all objects in the given Lua state
-(calling the corresponding garbage-collection metamethods, if any)
-and frees all dynamic memory used by this state.
-On several platforms, you may not need to call this function,
-because all resources are naturally released when the host program ends.
-On the other hand, long-running programs that create multiple states,
-such as daemons or web servers,
-might need to close states as soon as they are not needed.
-<hr><h3><a name="lua_compare"><code>lua_compare</code></a></h3><p>
-<span class="apii">[-0, +0, <em>e</em>]</span>
-<pre>int lua_compare (lua_State *L, int index1, int index2, int op);</pre>
-<p>
-Compares two Lua values.
-Returns 1 if the value at index <code>index1</code> satisfies <code>op</code>
-when compared with the value at index <code>index2</code>,
-following the semantics of the corresponding Lua operator
-(that is, it may call metamethods).
-Otherwise returns&nbsp;0.
-Also returns&nbsp;0 if any of the indices is non valid.
-<p>
-The value of <code>op</code> must be one of the following constants:
-<ul>
-<li><b><a name="pdf-LUA_OPEQ"><code>LUA_OPEQ</code></a>: </b> compares for equality (<code>==</code>)</li>
-<li><b><a name="pdf-LUA_OPLT"><code>LUA_OPLT</code></a>: </b> compares for less than (<code>&lt;</code>)</li>
-<li><b><a name="pdf-LUA_OPLE"><code>LUA_OPLE</code></a>: </b> compares for less or equal (<code>&lt;=</code>)</li>
-</ul>
-<hr><h3><a name="lua_concat"><code>lua_concat</code></a></h3><p>
-<span class="apii">[-n, +1, <em>e</em>]</span>
-<pre>void lua_concat (lua_State *L, int n);</pre>
-<p>
-Concatenates the <code>n</code> values at the top of the stack,
-pops them, and leaves the result at the top.
-If <code>n</code>&nbsp;is&nbsp;1, the result is the single value on the stack
-(that is, the function does nothing);
-if <code>n</code> is 0, the result is the empty string.
-Concatenation is performed following the usual semantics of Lua
-(see <a href="#3.4.5">&sect;3.4.5</a>).
-<hr><h3><a name="lua_copy"><code>lua_copy</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void lua_copy (lua_State *L, int fromidx, int toidx);</pre>
-<p>
-Moves the element at index <code>fromidx</code>
-into the valid index <code>toidx</code>
-without shifting any element
-(therefore replacing the value at that position).
-<hr><h3><a name="lua_createtable"><code>lua_createtable</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void lua_createtable (lua_State *L, int narr, int nrec);</pre>
-<p>
-Creates a new empty table and pushes it onto the stack.
-Parameter <code>narr</code> is a hint for how many elements the table
-will have as a sequence;
-parameter <code>nrec</code> is a hint for how many other elements
-the table will have.
-Lua may use these hints to preallocate memory for the new table.
-This pre-allocation is useful for performance when you know in advance
-how many elements the table will have.
-Otherwise you can use the function <a href="#lua_newtable"><code>lua_newtable</code></a>.
-<hr><h3><a name="lua_dump"><code>lua_dump</code></a></h3><p>
-<span class="apii">[-0, +0, <em>e</em>]</span>
-<pre>int lua_dump (lua_State *L, lua_Writer writer, void *data);</pre>
-<p>
-Dumps a function as a binary chunk.
-Receives a Lua function on the top of the stack
-and produces a binary chunk that,
-if loaded again,
-results in a function equivalent to the one dumped.
-As it produces parts of the chunk,
-<a href="#lua_dump"><code>lua_dump</code></a> calls function <code>writer</code> (see <a href="#lua_Writer"><code>lua_Writer</code></a>)
-with the given <code>data</code>
-to write them.
-<p>
-The value returned is the error code returned by the last
-call to the writer;
-0&nbsp;means no errors.
-<p>
-This function does not pop the Lua function from the stack.
-<hr><h3><a name="lua_error"><code>lua_error</code></a></h3><p>
-<span class="apii">[-1, +0, <em>v</em>]</span>
-<pre>int lua_error (lua_State *L);</pre>
-<p>
-Generates a Lua error.
-The error message (which can actually be a Lua value of any type)
-must be on the stack top.
-This function does a long jump,
-and therefore never returns
-(see <a href="#luaL_error"><code>luaL_error</code></a>).
-<hr><h3><a name="lua_gc"><code>lua_gc</code></a></h3><p>
-<span class="apii">[-0, +0, <em>e</em>]</span>
-<pre>int lua_gc (lua_State *L, int what, int data);</pre>
-<p>
-Controls the garbage collector.
-<p>
-This function performs several tasks,
-according to the value of the parameter <code>what</code>:
-<ul>
-<li><b><code>LUA_GCSTOP</code>: </b>
-stops the garbage collector.
-</li>
-<li><b><code>LUA_GCRESTART</code>: </b>
-restarts the garbage collector.
-</li>
-<li><b><code>LUA_GCCOLLECT</code>: </b>
-performs a full garbage-collection cycle.
-</li>
-<li><b><code>LUA_GCCOUNT</code>: </b>
-returns the current amount of memory (in Kbytes) in use by Lua.
-</li>
-<li><b><code>LUA_GCCOUNTB</code>: </b>
-returns the remainder of dividing the current amount of bytes of
-memory in use by Lua by 1024.
-</li>
-<li><b><code>LUA_GCSTEP</code>: </b>
-performs an incremental step of garbage collection.
-The step "size" is controlled by <code>data</code>
-(larger values mean more steps) in a non-specified way.
-If you want to control the step size
-you must experimentally tune the value of <code>data</code>.
-The function returns 1 if the step finished a
-garbage-collection cycle.
-</li>
-<li><b><code>LUA_GCSETPAUSE</code>: </b>
-sets <code>data</code> as the new value
-for the <em>pause</em> of the collector (see <a href="#2.5">&sect;2.5</a>).
-The function returns the previous value of the pause.
-</li>
-<li><b><code>LUA_GCSETSTEPMUL</code>: </b>
-sets <code>data</code> as the new value for the <em>step multiplier</em> of
-the collector (see <a href="#2.5">&sect;2.5</a>).
-The function returns the previous value of the step multiplier.
-</li>
-<li><b><code>LUA_GCISRUNNING</code>: </b>
-returns a boolean that tells whether the collector is running
-(i.e., not stopped).
-</li>
-<li><b><code>LUA_GCGEN</code>: </b>
-changes the collector to generational mode
-(see <a href="#2.5">&sect;2.5</a>).
-</li>
-<li><b><code>LUA_GCINC</code>: </b>
-changes the collector to incremental mode.
-This is the default mode.
-</li>
-</ul>
-<p>
-For more details about these options,
-see <a href="#pdf-collectgarbage"><code>collectgarbage</code></a>.
-<hr><h3><a name="lua_getallocf"><code>lua_getallocf</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_Alloc lua_getallocf (lua_State *L, void **ud);</pre>
-<p>
-Returns the memory-allocation function of a given state.
-If <code>ud</code> is not <code>NULL</code>, Lua stores in <code>*ud</code> the
-opaque pointer passed to <a href="#lua_newstate"><code>lua_newstate</code></a>.
-<hr><h3><a name="lua_getctx"><code>lua_getctx</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_getctx (lua_State *L, int *ctx);</pre>
-<p>
-This function is called by a continuation function (see <a href="#4.7">&sect;4.7</a>)
-to retrieve the status of the thread and a context information.
-<p>
-When called in the original function,
-<a href="#lua_getctx"><code>lua_getctx</code></a> always returns <a href="#pdf-LUA_OK"><code>LUA_OK</code></a>
-and does not change the value of its argument <code>ctx</code>.
-When called inside a continuation function,
-<a href="#lua_getctx"><code>lua_getctx</code></a> returns <a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a> and sets
-the value of <code>ctx</code> to be the context information
-(the value passed as the <code>ctx</code> argument
-to the callee together with the continuation function).
-<p>
-When the callee is <a href="#lua_pcallk"><code>lua_pcallk</code></a>,
-Lua may also call its continuation function
-to handle errors during the call.
-That is, upon an error in the function called by <a href="#lua_pcallk"><code>lua_pcallk</code></a>,
-Lua may not return to the original function
-but instead may call the continuation function.
-In that case, a call to <a href="#lua_getctx"><code>lua_getctx</code></a> will return the error code
-(the value that would be returned by <a href="#lua_pcallk"><code>lua_pcallk</code></a>);
-the value of <code>ctx</code> will be set to the context information,
-as in the case of a yield.
-<hr><h3><a name="lua_getfield"><code>lua_getfield</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void lua_getfield (lua_State *L, int index, const char *k);</pre>
-<p>
-Pushes onto the stack the value <code>t[k]</code>,
-where <code>t</code> is the value at the given index.
-As in Lua, this function may trigger a metamethod
-for the "index" event (see <a href="#2.4">&sect;2.4</a>).
-<hr><h3><a name="lua_getglobal"><code>lua_getglobal</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void lua_getglobal (lua_State *L, const char *name);</pre>
-<p>
-Pushes onto the stack the value of the global <code>name</code>.
-<hr><h3><a name="lua_getmetatable"><code>lua_getmetatable</code></a></h3><p>
-<span class="apii">[-0, +(0|1), &ndash;]</span>
-<pre>int lua_getmetatable (lua_State *L, int index);</pre>
-<p>
-Pushes onto the stack the metatable of the value at the given index.
-If the value does not have a metatable,
-the function returns&nbsp;0 and pushes nothing on the stack.
-<hr><h3><a name="lua_gettable"><code>lua_gettable</code></a></h3><p>
-<span class="apii">[-1, +1, <em>e</em>]</span>
-<pre>void lua_gettable (lua_State *L, int index);</pre>
-<p>
-Pushes onto the stack the value <code>t[k]</code>,
-where <code>t</code> is the value at the given index
-and <code>k</code> is the value at the top of the stack.
-<p>
-This function pops the key from the stack
-(putting the resulting value in its place).
-As in Lua, this function may trigger a metamethod
-for the "index" event (see <a href="#2.4">&sect;2.4</a>).
-<hr><h3><a name="lua_gettop"><code>lua_gettop</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_gettop (lua_State *L);</pre>
-<p>
-Returns the index of the top element in the stack.
-Because indices start at&nbsp;1,
-this result is equal to the number of elements in the stack
-(and so 0&nbsp;means an empty stack).
-<hr><h3><a name="lua_getuservalue"><code>lua_getuservalue</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_getuservalue (lua_State *L, int index);</pre>
-<p>
-Pushes onto the stack the Lua value associated with the userdata
-at the given index.
-This Lua value must be a table or <b>nil</b>.
-<hr><h3><a name="lua_insert"><code>lua_insert</code></a></h3><p>
-<span class="apii">[-1, +1, &ndash;]</span>
-<pre>void lua_insert (lua_State *L, int index);</pre>
-<p>
-Moves the top element into the given valid index,
-shifting up the elements above this index to open space.
-This function cannot be called with a pseudo-index,
-because a pseudo-index is not an actual stack position.
-<hr><h3><a name="lua_Integer"><code>lua_Integer</code></a></h3>
-<pre>typedef ptrdiff_t lua_Integer;</pre>
-<p>
-The type used by the Lua API to represent signed integral values.
-<p>
-By default it is a <code>ptrdiff_t</code>,
-which is usually the largest signed integral type the machine handles
-"comfortably".
-<hr><h3><a name="lua_isboolean"><code>lua_isboolean</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isboolean (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a boolean,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_iscfunction"><code>lua_iscfunction</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_iscfunction (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a C&nbsp;function,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isfunction"><code>lua_isfunction</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isfunction (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a function
-(either C or Lua), and 0&nbsp;otherwise.
-<hr><h3><a name="lua_islightuserdata"><code>lua_islightuserdata</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_islightuserdata (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a light userdata,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isnil"><code>lua_isnil</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isnil (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is <b>nil</b>,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isnone"><code>lua_isnone</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isnone (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the given index is not valid,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isnoneornil"><code>lua_isnoneornil</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isnoneornil (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the given index is not valid
-or if the value at this index is <b>nil</b>,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isnumber"><code>lua_isnumber</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isnumber (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a number
-or a string convertible to a number,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isstring"><code>lua_isstring</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isstring (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a string
-or a number (which is always convertible to a string),
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_istable"><code>lua_istable</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_istable (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a table,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isthread"><code>lua_isthread</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isthread (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a thread,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isuserdata"><code>lua_isuserdata</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isuserdata (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a userdata
-(either full or light), and 0&nbsp;otherwise.
-<hr><h3><a name="lua_len"><code>lua_len</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void lua_len (lua_State *L, int index);</pre>
-<p>
-Returns the "length" of the value at the given index;
-it is equivalent to the '<code>#</code>' operator in Lua (see <a href="#3.4.6">&sect;3.4.6</a>).
-The result is pushed on the stack.
-<hr><h3><a name="lua_load"><code>lua_load</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>int lua_load (lua_State *L,
-lua_Reader reader,
-void *data,
-const char *source,
-const char *mode);</pre>
-<p>
-Loads a Lua chunk (without running it).
-If there are no errors,
-<code>lua_load</code> pushes the compiled chunk as a Lua
-function on top of the stack.
-Otherwise, it pushes an error message.
-<p>
-The return values of <code>lua_load</code> are:
-<ul>
-<li><b><a href="#pdf-LUA_OK"><code>LUA_OK</code></a>: </b> no errors;</li>
-<li><b><a name="pdf-LUA_ERRSYNTAX"><code>LUA_ERRSYNTAX</code></a>: </b>
-syntax error during precompilation;</li>
-<li><b><a href="#pdf-LUA_ERRMEM"><code>LUA_ERRMEM</code></a>: </b>
-memory allocation error;</li>
-<li><b><a href="#pdf-LUA_ERRGCMM"><code>LUA_ERRGCMM</code></a>: </b>
-error while running a <code>__gc</code> metamethod.
-(This error has no relation with the chunk being loaded.
-It is generated by the garbage collector.)
-</li>
-</ul>
-<p>
-The <code>lua_load</code> function uses a user-supplied <code>reader</code> function
-to read the chunk (see <a href="#lua_Reader"><code>lua_Reader</code></a>).
-The <code>data</code> argument is an opaque value passed to the reader function.
-<p>
-The <code>source</code> argument gives a name to the chunk,
-which is used for error messages and in debug information (see <a href="#4.9">&sect;4.9</a>).
-<p>
-<code>lua_load</code> automatically detects whether the chunk is text or binary
-and loads it accordingly (see program <code>luac</code>).
-The string <code>mode</code> works as in function <a href="#pdf-load"><code>load</code></a>,
-with the addition that
-a <code>NULL</code> value is equivalent to the string "<code>bt</code>".
-<p>
-<code>lua_load</code> uses the stack internally,
-so the reader function should always leave the stack
-unmodified when returning.
-<p>
-If the resulting function has one upvalue,
-this upvalue is set to the value of the global environment
-stored at index <code>LUA_RIDX_GLOBALS</code> in the registry (see <a href="#4.5">&sect;4.5</a>).
-When loading main chunks,
-this upvalue will be the <code>_ENV</code> variable (see <a href="#2.2">&sect;2.2</a>).
-<hr><h3><a name="lua_newstate"><code>lua_newstate</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_State *lua_newstate (lua_Alloc f, void *ud);</pre>
-<p>
-Creates a new thread running in a new, independent state.
-Returns <code>NULL</code> if cannot create the thread or the state
-(due to lack of memory).
-The argument <code>f</code> is the allocator function;
-Lua does all memory allocation for this state through this function.
-The second argument, <code>ud</code>, is an opaque pointer that Lua
-passes to the allocator in every call.
-<hr><h3><a name="lua_newtable"><code>lua_newtable</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void lua_newtable (lua_State *L);</pre>
-<p>
-Creates a new empty table and pushes it onto the stack.
-It is equivalent to <code>lua_createtable(L, 0, 0)</code>.
-<hr><h3><a name="lua_newthread"><code>lua_newthread</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>lua_State *lua_newthread (lua_State *L);</pre>
-<p>
-Creates a new thread, pushes it on the stack,
-and returns a pointer to a <a href="#lua_State"><code>lua_State</code></a> that represents this new thread.
-The new thread returned by this function shares with the original thread
-its global environment,
-but has an independent execution stack.
-<p>
-There is no explicit function to close or to destroy a thread.
-Threads are subject to garbage collection,
-like any Lua object.
-<hr><h3><a name="lua_newuserdata"><code>lua_newuserdata</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void *lua_newuserdata (lua_State *L, size_t size);</pre>
-<p>
-This function allocates a new block of memory with the given size,
-pushes onto the stack a new full userdata with the block address,
-and returns this address.
-The host program can freely use this memory.
-<hr><h3><a name="lua_next"><code>lua_next</code></a></h3><p>
-<span class="apii">[-1, +(2|0), <em>e</em>]</span>
-<pre>int lua_next (lua_State *L, int index);</pre>
-<p>
-Pops a key from the stack,
-and pushes a key&ndash;value pair from the table at the given index
-(the "next" pair after the given key).
-If there are no more elements in the table,
-then <a href="#lua_next"><code>lua_next</code></a> returns 0 (and pushes nothing).
-<p>
-A typical traversal looks like this:
-<pre>
-/* table is in the stack at index 't' */
-lua_pushnil(L);  /* first key */
-while (lua_next(L, t) != 0) {
-/* uses 'key' (at index -2) and 'value' (at index -1) */
-printf("%s - %s\n",
-lua_typename(L, lua_type(L, -2)),
-lua_typename(L, lua_type(L, -1)));
-/* removes 'value'; keeps 'key' for next iteration */
-lua_pop(L, 1);
-}
-</pre>
-<p>
-While traversing a table,
-do not call <a href="#lua_tolstring"><code>lua_tolstring</code></a> directly on a key,
-unless you know that the key is actually a string.
-Recall that <a href="#lua_tolstring"><code>lua_tolstring</code></a> may change
-the value at the given index;
-this confuses the next call to <a href="#lua_next"><code>lua_next</code></a>.
-<p>
-See function <a href="#pdf-next"><code>next</code></a> for the caveats of modifying
-the table during its traversal.
-<hr><h3><a name="lua_Number"><code>lua_Number</code></a></h3>
-<pre>typedef double lua_Number;</pre>
-<p>
-The type of numbers in Lua.
-By default, it is double, but that can be changed in <code>luaconf.h</code>.
-Through this configuration file you can change
-Lua to operate with another type for numbers (e.g., float or long).
-<hr><h3><a name="lua_pcall"><code>lua_pcall</code></a></h3><p>
-<span class="apii">[-(nargs + 1), +(nresults|1), &ndash;]</span>
-<pre>int lua_pcall (lua_State *L, int nargs, int nresults, int msgh);</pre>
-<p>
-Calls a function in protected mode.
-<p>
-Both <code>nargs</code> and <code>nresults</code> have the same meaning as
-in <a href="#lua_call"><code>lua_call</code></a>.
-If there are no errors during the call,
-<a href="#lua_pcall"><code>lua_pcall</code></a> behaves exactly like <a href="#lua_call"><code>lua_call</code></a>.
-However, if there is any error,
-<a href="#lua_pcall"><code>lua_pcall</code></a> catches it,
-pushes a single value on the stack (the error message),
-and returns an error code.
-Like <a href="#lua_call"><code>lua_call</code></a>,
-<a href="#lua_pcall"><code>lua_pcall</code></a> always removes the function
-and its arguments from the stack.
-<p>
-If <code>msgh</code> is 0,
-then the error message returned on the stack
-is exactly the original error message.
-Otherwise, <code>msgh</code> is the stack index of a
-<em>message handler</em>.
-(In the current implementation, this index cannot be a pseudo-index.)
-In case of runtime errors,
-this function will be called with the error message
-and its return value will be the message
-returned on the stack by <a href="#lua_pcall"><code>lua_pcall</code></a>.
-<p>
-Typically, the message handler is used to add more debug
-information to the error message, such as a stack traceback.
-Such information cannot be gathered after the return of <a href="#lua_pcall"><code>lua_pcall</code></a>,
-since by then the stack has unwound.
-<p>
-The <a href="#lua_pcall"><code>lua_pcall</code></a> function returns one of the following codes
-(defined in <code>lua.h</code>):
-<ul>
-<li><b><a name="pdf-LUA_OK"><code>LUA_OK</code></a> (0): </b>
-success.</li>
-<li><b><a name="pdf-LUA_ERRRUN"><code>LUA_ERRRUN</code></a>: </b>
-a runtime error.
-</li>
-<li><b><a name="pdf-LUA_ERRMEM"><code>LUA_ERRMEM</code></a>: </b>
-memory allocation error.
-For such errors, Lua does not call the message handler.
-</li>
-<li><b><a name="pdf-LUA_ERRERR"><code>LUA_ERRERR</code></a>: </b>
-error while running the message handler.
-</li>
-<li><b><a name="pdf-LUA_ERRGCMM"><code>LUA_ERRGCMM</code></a>: </b>
-error while running a <code>__gc</code> metamethod.
-(This error typically has no relation with the function being called.
-It is generated by the garbage collector.)
-</li>
-</ul>
-<hr><h3><a name="lua_pcallk"><code>lua_pcallk</code></a></h3><p>
-<span class="apii">[-(nargs + 1), +(nresults|1), &ndash;]</span>
-<pre>int lua_pcallk (lua_State *L,
-int nargs,
-int nresults,
-int errfunc,
-int ctx,
-lua_CFunction k);</pre>
-<p>
-This function behaves exactly like <a href="#lua_pcall"><code>lua_pcall</code></a>,
-but allows the called function to yield (see <a href="#4.7">&sect;4.7</a>).
-<hr><h3><a name="lua_pop"><code>lua_pop</code></a></h3><p>
-<span class="apii">[-n, +0, &ndash;]</span>
-<pre>void lua_pop (lua_State *L, int n);</pre>
-<p>
-Pops <code>n</code> elements from the stack.
-<hr><h3><a name="lua_pushboolean"><code>lua_pushboolean</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushboolean (lua_State *L, int b);</pre>
-<p>
-Pushes a boolean value with value <code>b</code> onto the stack.
-<hr><h3><a name="lua_pushcclosure"><code>lua_pushcclosure</code></a></h3><p>
-<span class="apii">[-n, +1, <em>e</em>]</span>
-<pre>void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n);</pre>
-<p>
-Pushes a new C&nbsp;closure onto the stack.
-<p>
-When a C&nbsp;function is created,
-it is possible to associate some values with it,
-thus creating a C&nbsp;closure (see <a href="#4.4">&sect;4.4</a>);
-these values are then accessible to the function whenever it is called.
-To associate values with a C&nbsp;function,
-first these values should be pushed onto the stack
-(when there are multiple values, the first value is pushed first).
-Then <a href="#lua_pushcclosure"><code>lua_pushcclosure</code></a>
-is called to create and push the C&nbsp;function onto the stack,
-with the argument <code>n</code> telling how many values should be
-associated with the function.
-<a href="#lua_pushcclosure"><code>lua_pushcclosure</code></a> also pops these values from the stack.
-<p>
-The maximum value for <code>n</code> is 255.
-<p>
-When <code>n</code> is zero,
-this function creates a <em>light C function</em>,
-which is just a pointer to the C&nbsp;function.
-In that case, it never throws a memory error.
-<hr><h3><a name="lua_pushcfunction"><code>lua_pushcfunction</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushcfunction (lua_State *L, lua_CFunction f);</pre>
-<p>
-Pushes a C&nbsp;function onto the stack.
-This function receives a pointer to a C function
-and pushes onto the stack a Lua value of type <code>function</code> that,
-when called, invokes the corresponding C&nbsp;function.
-<p>
-Any function to be registered in Lua must
-follow the correct protocol to receive its parameters
-and return its results (see <a href="#lua_CFunction"><code>lua_CFunction</code></a>).
-<p>
-<code>lua_pushcfunction</code> is defined as a macro:
-<pre>
-#define lua_pushcfunction(L,f)  lua_pushcclosure(L,f,0)
-</pre><p>
-Note that <code>f</code> is used twice.
-<hr><h3><a name="lua_pushfstring"><code>lua_pushfstring</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>const char *lua_pushfstring (lua_State *L, const char *fmt, ...);</pre>
-<p>
-Pushes onto the stack a formatted string
-and returns a pointer to this string.
-It is similar to the ANSI&nbsp;C function <code>sprintf</code>,
-but has some important differences:
-<ul>
-<li>
-You do not have to allocate space for the result:
-the result is a Lua string and Lua takes care of memory allocation
-(and deallocation, through garbage collection).
-</li>
-<li>
-The conversion specifiers are quite restricted.
-There are no flags, widths, or precisions.
-The conversion specifiers can only be
-'<code>%%</code>' (inserts a '<code>%</code>' in the string),
-'<code>%s</code>' (inserts a zero-terminated string, with no size restrictions),
-'<code>%f</code>' (inserts a <a href="#lua_Number"><code>lua_Number</code></a>),
-'<code>%p</code>' (inserts a pointer as a hexadecimal numeral),
-'<code>%d</code>' (inserts an <code>int</code>), and
-'<code>%c</code>' (inserts an <code>int</code> as a byte).
-</li>
-</ul>
-<hr><h3><a name="lua_pushglobaltable"><code>lua_pushglobaltable</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushglobaltable (lua_State *L);</pre>
-<p>
-Pushes the global environment onto the stack.
-<hr><h3><a name="lua_pushinteger"><code>lua_pushinteger</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushinteger (lua_State *L, lua_Integer n);</pre>
-<p>
-Pushes a number with value <code>n</code> onto the stack.
-<hr><h3><a name="lua_pushlightuserdata"><code>lua_pushlightuserdata</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushlightuserdata (lua_State *L, void *p);</pre>
-<p>
-Pushes a light userdata onto the stack.
-<p>
-Userdata represent C&nbsp;values in Lua.
-A <em>light userdata</em> represents a pointer, a <code>void*</code>.
-It is a value (like a number):
-you do not create it, it has no individual metatable,
-and it is not collected (as it was never created).
-A light userdata is equal to "any"
-light userdata with the same C&nbsp;address.
-<hr><h3><a name="lua_pushliteral"><code>lua_pushliteral</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>const char *lua_pushliteral (lua_State *L, const char *s);</pre>
-<p>
-This macro is equivalent to <a href="#lua_pushlstring"><code>lua_pushlstring</code></a>,
-but can be used only when <code>s</code> is a literal string.
-It automatically provides the string length.
-<hr><h3><a name="lua_pushlstring"><code>lua_pushlstring</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>const char *lua_pushlstring (lua_State *L, const char *s, size_t len);</pre>
-<p>
-Pushes the string pointed to by <code>s</code> with size <code>len</code>
-onto the stack.
-Lua makes (or reuses) an internal copy of the given string,
-so the memory at <code>s</code> can be freed or reused immediately after
-the function returns.
-The string can contain any binary data,
-including embedded zeros.
-<p>
-Returns a pointer to the internal copy of the string.
-<hr><h3><a name="lua_pushnil"><code>lua_pushnil</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushnil (lua_State *L);</pre>
-<p>
-Pushes a nil value onto the stack.
-<hr><h3><a name="lua_pushnumber"><code>lua_pushnumber</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushnumber (lua_State *L, lua_Number n);</pre>
-<p>
-Pushes a number with value <code>n</code> onto the stack.
-<hr><h3><a name="lua_pushstring"><code>lua_pushstring</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>const char *lua_pushstring (lua_State *L, const char *s);</pre>
-<p>
-Pushes the zero-terminated string pointed to by <code>s</code>
-onto the stack.
-Lua makes (or reuses) an internal copy of the given string,
-so the memory at <code>s</code> can be freed or reused immediately after
-the function returns.
-<p>
-Returns a pointer to the internal copy of the string.
-<p>
-If <code>s</code> is <code>NULL</code>, pushes <b>nil</b> and returns <code>NULL</code>.
-<hr><h3><a name="lua_pushthread"><code>lua_pushthread</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>int lua_pushthread (lua_State *L);</pre>
-<p>
-Pushes the thread represented by <code>L</code> onto the stack.
-Returns 1 if this thread is the main thread of its state.
-<hr><h3><a name="lua_pushunsigned"><code>lua_pushunsigned</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushunsigned (lua_State *L, lua_Unsigned n);</pre>
-<p>
-Pushes a number with value <code>n</code> onto the stack.
-<hr><h3><a name="lua_pushvalue"><code>lua_pushvalue</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushvalue (lua_State *L, int index);</pre>
-<p>
-Pushes a copy of the element at the given index
-onto the stack.
-<hr><h3><a name="lua_pushvfstring"><code>lua_pushvfstring</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>const char *lua_pushvfstring (lua_State *L,
-const char *fmt,
-va_list argp);</pre>
-<p>
-Equivalent to <a href="#lua_pushfstring"><code>lua_pushfstring</code></a>, except that it receives a <code>va_list</code>
-instead of a variable number of arguments.
-<hr><h3><a name="lua_rawequal"><code>lua_rawequal</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_rawequal (lua_State *L, int index1, int index2);</pre>
-<p>
-Returns 1 if the two values in indices <code>index1</code> and
-<code>index2</code> are primitively equal
-(that is, without calling metamethods).
-Otherwise returns&nbsp;0.
-Also returns&nbsp;0 if any of the indices are non valid.
-<hr><h3><a name="lua_rawget"><code>lua_rawget</code></a></h3><p>
-<span class="apii">[-1, +1, &ndash;]</span>
-<pre>void lua_rawget (lua_State *L, int index);</pre>
-<p>
-Similar to <a href="#lua_gettable"><code>lua_gettable</code></a>, but does a raw access
-(i.e., without metamethods).
-<hr><h3><a name="lua_rawgeti"><code>lua_rawgeti</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_rawgeti (lua_State *L, int index, int n);</pre>
-<p>
-Pushes onto the stack the value <code>t[n]</code>,
-where <code>t</code> is the table at the given index.
-The access is raw;
-that is, it does not invoke metamethods.
-<hr><h3><a name="lua_rawgetp"><code>lua_rawgetp</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_rawgetp (lua_State *L, int index, const void *p);</pre>
-<p>
-Pushes onto the stack the value <code>t[k]</code>,
-where <code>t</code> is the table at the given index and
-<code>k</code> is the pointer <code>p</code> represented as a light userdata.
-The access is raw;
-that is, it does not invoke metamethods.
-<hr><h3><a name="lua_rawlen"><code>lua_rawlen</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>size_t lua_rawlen (lua_State *L, int index);</pre>
-<p>
-Returns the raw "length" of the value at the given index:
-for strings, this is the string length;
-for tables, this is the result of the length operator ('<code>#</code>')
-with no metamethods;
-for userdata, this is the size of the block of memory allocated
-for the userdata;
-for other values, it is&nbsp;0.
-<hr><h3><a name="lua_rawset"><code>lua_rawset</code></a></h3><p>
-<span class="apii">[-2, +0, <em>e</em>]</span>
-<pre>void lua_rawset (lua_State *L, int index);</pre>
-<p>
-Similar to <a href="#lua_settable"><code>lua_settable</code></a>, but does a raw assignment
-(i.e., without metamethods).
-<hr><h3><a name="lua_rawseti"><code>lua_rawseti</code></a></h3><p>
-<span class="apii">[-1, +0, <em>e</em>]</span>
-<pre>void lua_rawseti (lua_State *L, int index, int n);</pre>
-<p>
-Does the equivalent of <code>t[n] = v</code>,
-where <code>t</code> is the table at the given index
-and <code>v</code> is the value at the top of the stack.
-<p>
-This function pops the value from the stack.
-The assignment is raw;
-that is, it does not invoke metamethods.
-<hr><h3><a name="lua_rawsetp"><code>lua_rawsetp</code></a></h3><p>
-<span class="apii">[-1, +0, <em>e</em>]</span>
-<pre>void lua_rawsetp (lua_State *L, int index, const void *p);</pre>
-<p>
-Does the equivalent of <code>t[k] = v</code>,
-where <code>t</code> is the table at the given index,
-<code>k</code> is the pointer <code>p</code> represented as a light userdata,
-and <code>v</code> is the value at the top of the stack.
-<p>
-This function pops the value from the stack.
-The assignment is raw;
-that is, it does not invoke metamethods.
-<hr><h3><a name="lua_Reader"><code>lua_Reader</code></a></h3>
-<pre>typedef const char * (*lua_Reader) (lua_State *L,
-void *data,
-size_t *size);</pre>
-<p>
-The reader function used by <a href="#lua_load"><code>lua_load</code></a>.
-Every time it needs another piece of the chunk,
-<a href="#lua_load"><code>lua_load</code></a> calls the reader,
-passing along its <code>data</code> parameter.
-The reader must return a pointer to a block of memory
-with a new piece of the chunk
-and set <code>size</code> to the block size.
-The block must exist until the reader function is called again.
-To signal the end of the chunk,
-the reader must return <code>NULL</code> or set <code>size</code> to zero.
-The reader function may return pieces of any size greater than zero.
-<hr><h3><a name="lua_register"><code>lua_register</code></a></h3><p>
-<span class="apii">[-0, +0, <em>e</em>]</span>
-<pre>void lua_register (lua_State *L, const char *name, lua_CFunction f);</pre>
-<p>
-Sets the C function <code>f</code> as the new value of global <code>name</code>.
-It is defined as a macro:
-<pre>
-#define lua_register(L,n,f) \
-(lua_pushcfunction(L, f), lua_setglobal(L, n))
-</pre>
-<hr><h3><a name="lua_remove"><code>lua_remove</code></a></h3><p>
-<span class="apii">[-1, +0, &ndash;]</span>
-<pre>void lua_remove (lua_State *L, int index);</pre>
-<p>
-Removes the element at the given valid index,
-shifting down the elements above this index to fill the gap.
-This function cannot be called with a pseudo-index,
-because a pseudo-index is not an actual stack position.
-<hr><h3><a name="lua_replace"><code>lua_replace</code></a></h3><p>
-<span class="apii">[-1, +0, &ndash;]</span>
-<pre>void lua_replace (lua_State *L, int index);</pre>
-<p>
-Moves the top element into the given valid index
-without shifting any element
-(therefore replacing the value at the given index),
-and then pops the top element.
-<hr><h3><a name="lua_resume"><code>lua_resume</code></a></h3><p>
-<span class="apii">[-?, +?, &ndash;]</span>
-<pre>int lua_resume (lua_State *L, lua_State *from, int nargs);</pre>
-<p>
-Starts and resumes a coroutine in a given thread.
-<p>
-To start a coroutine,
-you push onto the thread stack the main function plus any arguments;
-then you call <a href="#lua_resume"><code>lua_resume</code></a>,
-with <code>nargs</code> being the number of arguments.
-This call returns when the coroutine suspends or finishes its execution.
-When it returns, the stack contains all values passed to <a href="#lua_yield"><code>lua_yield</code></a>,
-or all values returned by the body function.
-<a href="#lua_resume"><code>lua_resume</code></a> returns
-<a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a> if the coroutine yields,
-<a href="#pdf-LUA_OK"><code>LUA_OK</code></a> if the coroutine finishes its execution
-without errors,
-or an error code in case of errors (see <a href="#lua_pcall"><code>lua_pcall</code></a>).
-<p>
-In case of errors,
-the stack is not unwound,
-so you can use the debug API over it.
-The error message is on the top of the stack.
-<p>
-To resume a coroutine,
-you remove any results from the last <a href="#lua_yield"><code>lua_yield</code></a>,
-put on its stack only the values to
-be passed as results from <code>yield</code>,
-and then call <a href="#lua_resume"><code>lua_resume</code></a>.
-<p>
-The parameter <code>from</code> represents the coroutine that is resuming <code>L</code>.
-If there is no such coroutine,
-this parameter can be <code>NULL</code>.
-<hr><h3><a name="lua_setallocf"><code>lua_setallocf</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void lua_setallocf (lua_State *L, lua_Alloc f, void *ud);</pre>
-<p>
-Changes the allocator function of a given state to <code>f</code>
-with user data <code>ud</code>.
-<hr><h3><a name="lua_setfield"><code>lua_setfield</code></a></h3><p>
-<span class="apii">[-1, +0, <em>e</em>]</span>
-<pre>void lua_setfield (lua_State *L, int index, const char *k);</pre>
-<p>
-Does the equivalent to <code>t[k] = v</code>,
-where <code>t</code> is the value at the given index
-and <code>v</code> is the value at the top of the stack.
-<p>
-This function pops the value from the stack.
-As in Lua, this function may trigger a metamethod
-for the "newindex" event (see <a href="#2.4">&sect;2.4</a>).
-<hr><h3><a name="lua_setglobal"><code>lua_setglobal</code></a></h3><p>
-<span class="apii">[-1, +0, <em>e</em>]</span>
-<pre>void lua_setglobal (lua_State *L, const char *name);</pre>
-<p>
-Pops a value from the stack and
-sets it as the new value of global <code>name</code>.
-<hr><h3><a name="lua_setmetatable"><code>lua_setmetatable</code></a></h3><p>
-<span class="apii">[-1, +0, &ndash;]</span>
-<pre>void lua_setmetatable (lua_State *L, int index);</pre>
-<p>
-Pops a table from the stack and
-sets it as the new metatable for the value at the given index.
-<hr><h3><a name="lua_settable"><code>lua_settable</code></a></h3><p>
-<span class="apii">[-2, +0, <em>e</em>]</span>
-<pre>void lua_settable (lua_State *L, int index);</pre>
-<p>
-Does the equivalent to <code>t[k] = v</code>,
-where <code>t</code> is the value at the given index,
-<code>v</code> is the value at the top of the stack,
-and <code>k</code> is the value just below the top.
-<p>
-This function pops both the key and the value from the stack.
-As in Lua, this function may trigger a metamethod
-for the "newindex" event (see <a href="#2.4">&sect;2.4</a>).
-<hr><h3><a name="lua_settop"><code>lua_settop</code></a></h3><p>
-<span class="apii">[-?, +?, &ndash;]</span>
-<pre>void lua_settop (lua_State *L, int index);</pre>
-<p>
-Accepts any index, or&nbsp;0,
-and sets the stack top to this index.
-If the new top is larger than the old one,
-then the new elements are filled with <b>nil</b>.
-If <code>index</code> is&nbsp;0, then all stack elements are removed.
-<hr><h3><a name="lua_setuservalue"><code>lua_setuservalue</code></a></h3><p>
-<span class="apii">[-1, +0, &ndash;]</span>
-<pre>void lua_setuservalue (lua_State *L, int index);</pre>
-<p>
-Pops a table or <b>nil</b> from the stack and sets it as
-the new value associated to the userdata at the given index.
-<hr><h3><a name="lua_State"><code>lua_State</code></a></h3>
-<pre>typedef struct lua_State lua_State;</pre>
-<p>
-An opaque structure that points to a thread and indirectly
-(through the thread) to the whole state of a Lua interpreter.
-The Lua library is fully reentrant:
-it has no global variables.
-All information about a state is accessible through this structure.
-<p>
-A pointer to this structure must be passed as the first argument to
-every function in the library, except to <a href="#lua_newstate"><code>lua_newstate</code></a>,
-which creates a Lua state from scratch.
-<hr><h3><a name="lua_status"><code>lua_status</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_status (lua_State *L);</pre>
-<p>
-Returns the status of the thread <code>L</code>.
-<p>
-The status can be 0 (<a href="#pdf-LUA_OK"><code>LUA_OK</code></a>) for a normal thread,
-an error code if the thread finished the execution
-of a <a href="#lua_resume"><code>lua_resume</code></a> with an error,
-or <a name="pdf-LUA_YIELD"><code>LUA_YIELD</code></a> if the thread is suspended.
-<p>
-You can only call functions in threads with status <a href="#pdf-LUA_OK"><code>LUA_OK</code></a>.
-You can resume threads with status <a href="#pdf-LUA_OK"><code>LUA_OK</code></a>
-(to start a new coroutine) or <a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a>
-(to resume a coroutine).
-<hr><h3><a name="lua_toboolean"><code>lua_toboolean</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_toboolean (lua_State *L, int index);</pre>
-<p>
-Converts the Lua value at the given index to a C&nbsp;boolean
-value (0&nbsp;or&nbsp;1).
-Like all tests in Lua,
-<a href="#lua_toboolean"><code>lua_toboolean</code></a> returns true for any Lua value
-different from <b>false</b> and <b>nil</b>;
-otherwise it returns false.
-(If you want to accept only actual boolean values,
-use <a href="#lua_isboolean"><code>lua_isboolean</code></a> to test the value's type.)
-<hr><h3><a name="lua_tocfunction"><code>lua_tocfunction</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_CFunction lua_tocfunction (lua_State *L, int index);</pre>
-<p>
-Converts a value at the given index to a C&nbsp;function.
-That value must be a C&nbsp;function;
-otherwise, returns <code>NULL</code>.
-<hr><h3><a name="lua_tointeger"><code>lua_tointeger</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_Integer lua_tointeger (lua_State *L, int index);</pre>
-<p>
-Equivalent to <a href="#lua_tointegerx"><code>lua_tointegerx</code></a> with <code>isnum</code> equal to <code>NULL</code>.
-<hr><h3><a name="lua_tointegerx"><code>lua_tointegerx</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_Integer lua_tointegerx (lua_State *L, int index, int *isnum);</pre>
-<p>
-Converts the Lua value at the given index
-to the signed integral type <a href="#lua_Integer"><code>lua_Integer</code></a>.
-The Lua value must be a number or a string convertible to a number
-(see <a href="#3.4.2">&sect;3.4.2</a>);
-otherwise, <code>lua_tointegerx</code> returns&nbsp;0.
-<p>
-If the number is not an integer,
-it is truncated in some non-specified way.
-<p>
-If <code>isnum</code> is not <code>NULL</code>,
-its referent is assigned a boolean value that
-indicates whether the operation succeeded.
-<hr><h3><a name="lua_tolstring"><code>lua_tolstring</code></a></h3><p>
-<span class="apii">[-0, +0, <em>e</em>]</span>
-<pre>const char *lua_tolstring (lua_State *L, int index, size_t *len);</pre>
-<p>
-Converts the Lua value at the given index to a C&nbsp;string.
-If <code>len</code> is not <code>NULL</code>,
-it also sets <code>*len</code> with the string length.
-The Lua value must be a string or a number;
-otherwise, the function returns <code>NULL</code>.
-If the value is a number,
-then <code>lua_tolstring</code> also
-<em>changes the actual value in the stack to a string</em>.
-(This change confuses <a href="#lua_next"><code>lua_next</code></a>
-when <code>lua_tolstring</code> is applied to keys during a table traversal.)
-<p>
-<code>lua_tolstring</code> returns a fully aligned pointer
-to a string inside the Lua state.
-This string always has a zero ('<code>\0</code>')
-after its last character (as in&nbsp;C),
-but can contain other zeros in its body.
-Because Lua has garbage collection,
-there is no guarantee that the pointer returned by <code>lua_tolstring</code>
-will be valid after the corresponding value is removed from the stack.
-<hr><h3><a name="lua_tonumber"><code>lua_tonumber</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_Number lua_tonumber (lua_State *L, int index);</pre>
-<p>
-Equivalent to <a href="#lua_tonumberx"><code>lua_tonumberx</code></a> with <code>isnum</code> equal to <code>NULL</code>.
-<hr><h3><a name="lua_tonumberx"><code>lua_tonumberx</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_Number lua_tonumberx (lua_State *L, int index, int *isnum);</pre>
-<p>
-Converts the Lua value at the given index
-to the C&nbsp;type <a href="#lua_Number"><code>lua_Number</code></a> (see <a href="#lua_Number"><code>lua_Number</code></a>).
-The Lua value must be a number or a string convertible to a number
-(see <a href="#3.4.2">&sect;3.4.2</a>);
-otherwise, <a href="#lua_tonumberx"><code>lua_tonumberx</code></a> returns&nbsp;0.
-<p>
-If <code>isnum</code> is not <code>NULL</code>,
-its referent is assigned a boolean value that
-indicates whether the operation succeeded.
-<hr><h3><a name="lua_topointer"><code>lua_topointer</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>const void *lua_topointer (lua_State *L, int index);</pre>
-<p>
-Converts the value at the given index to a generic
-C&nbsp;pointer (<code>void*</code>).
-The value can be a userdata, a table, a thread, or a function;
-otherwise, <code>lua_topointer</code> returns <code>NULL</code>.
-Different objects will give different pointers.
-There is no way to convert the pointer back to its original value.
-<p>
-Typically this function is used only for debug information.
-<hr><h3><a name="lua_tostring"><code>lua_tostring</code></a></h3><p>
-<span class="apii">[-0, +0, <em>e</em>]</span>
-<pre>const char *lua_tostring (lua_State *L, int index);</pre>
-<p>
-Equivalent to <a href="#lua_tolstring"><code>lua_tolstring</code></a> with <code>len</code> equal to <code>NULL</code>.
-<hr><h3><a name="lua_tothread"><code>lua_tothread</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_State *lua_tothread (lua_State *L, int index);</pre>
-<p>
-Converts the value at the given index to a Lua thread
-(represented as <code>lua_State*</code>).
-This value must be a thread;
-otherwise, the function returns <code>NULL</code>.
-<hr><h3><a name="lua_tounsigned"><code>lua_tounsigned</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_Unsigned lua_tounsigned (lua_State *L, int index);</pre>
-<p>
-Equivalent to <a href="#lua_tounsignedx"><code>lua_tounsignedx</code></a> with <code>isnum</code> equal to <code>NULL</code>.
-<hr><h3><a name="lua_tounsignedx"><code>lua_tounsignedx</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_Unsigned lua_tounsignedx (lua_State *L, int index, int *isnum);</pre>
-<p>
-Converts the Lua value at the given index
-to the unsigned integral type <a href="#lua_Unsigned"><code>lua_Unsigned</code></a>.
-The Lua value must be a number or a string convertible to a number
-(see <a href="#3.4.2">&sect;3.4.2</a>);
-otherwise, <code>lua_tounsignedx</code> returns&nbsp;0.
-<p>
-If the number is not an integer,
-it is truncated in some non-specified way.
-If the number is outside the range of representable values,
-it is normalized to the remainder of its division by
-one more than the maximum representable value.
-<p>
-If <code>isnum</code> is not <code>NULL</code>,
-its referent is assigned a boolean value that
-indicates whether the operation succeeded.
-<hr><h3><a name="lua_touserdata"><code>lua_touserdata</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void *lua_touserdata (lua_State *L, int index);</pre>
-<p>
-If the value at the given index is a full userdata,
-returns its block address.
-If the value is a light userdata,
-returns its pointer.
-Otherwise, returns <code>NULL</code>.
-<hr><h3><a name="lua_type"><code>lua_type</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_type (lua_State *L, int index);</pre>
-<p>
-Returns the type of the value in the given valid index,
-or <code>LUA_TNONE</code> for a non-valid (but acceptable) index.
-The types returned by <a href="#lua_type"><code>lua_type</code></a> are coded by the following constants
-defined in <code>lua.h</code>:
-<a name="pdf-LUA_TNIL"><code>LUA_TNIL</code></a>,
-<a name="pdf-LUA_TNUMBER"><code>LUA_TNUMBER</code></a>,
-<a name="pdf-LUA_TBOOLEAN"><code>LUA_TBOOLEAN</code></a>,
-<a name="pdf-LUA_TSTRING"><code>LUA_TSTRING</code></a>,
-<a name="pdf-LUA_TTABLE"><code>LUA_TTABLE</code></a>,
-<a name="pdf-LUA_TFUNCTION"><code>LUA_TFUNCTION</code></a>,
-<a name="pdf-LUA_TUSERDATA"><code>LUA_TUSERDATA</code></a>,
-<a name="pdf-LUA_TTHREAD"><code>LUA_TTHREAD</code></a>,
-and
-<a name="pdf-LUA_TLIGHTUSERDATA"><code>LUA_TLIGHTUSERDATA</code></a>.
-<hr><h3><a name="lua_typename"><code>lua_typename</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>const char *lua_typename (lua_State *L, int tp);</pre>
-<p>
-Returns the name of the type encoded by the value <code>tp</code>,
-which must be one the values returned by <a href="#lua_type"><code>lua_type</code></a>.
-<hr><h3><a name="lua_Unsigned"><code>lua_Unsigned</code></a></h3>
-<pre>typedef unsigned long lua_Unsigned;</pre>
-<p>
-The type used by the Lua API to represent unsigned integral values.
-It must have at least 32 bits.
-<p>
-By default it is an <code>unsigned int</code> or an <code>unsigned long</code>,
-whichever can hold 32-bit values.
-<hr><h3><a name="lua_upvalueindex"><code>lua_upvalueindex</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_upvalueindex (int i);</pre>
-<p>
-Returns the pseudo-index that represents the <code>i</code>-th upvalue of
-the running function (see <a href="#4.4">&sect;4.4</a>).
-<hr><h3><a name="lua_version"><code>lua_version</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>const lua_Number *lua_version (lua_State *L);</pre>
-<p>
-Returns the address of the version number stored in the Lua core.
-When called with a valid <a href="#lua_State"><code>lua_State</code></a>,
-returns the address of the version used to create that state.
-When called with <code>NULL</code>,
-returns the address of the version running the call.
-<hr><h3><a name="lua_Writer"><code>lua_Writer</code></a></h3>
-<pre>typedef int (*lua_Writer) (lua_State *L,
-const void* p,
-size_t sz,
-void* ud);</pre>
-<p>
-The type of the writer function used by <a href="#lua_dump"><code>lua_dump</code></a>.
-Every time it produces another piece of chunk,
-<a href="#lua_dump"><code>lua_dump</code></a> calls the writer,
-passing along the buffer to be written (<code>p</code>),
-its size (<code>sz</code>),
-and the <code>data</code> parameter supplied to <a href="#lua_dump"><code>lua_dump</code></a>.
-<p>
-The writer returns an error code:
-0&nbsp;means no errors;
-any other value means an error and stops <a href="#lua_dump"><code>lua_dump</code></a> from
-calling the writer again.
-<hr><h3><a name="lua_xmove"><code>lua_xmove</code></a></h3><p>
-<span class="apii">[-?, +?, &ndash;]</span>
-<pre>void lua_xmove (lua_State *from, lua_State *to, int n);</pre>
-<p>
-Exchange values between different threads of the same state.
-<p>
-This function pops <code>n</code> values from the stack <code>from</code>,
-and pushes them onto the stack <code>to</code>.
-<hr><h3><a name="lua_yield"><code>lua_yield</code></a></h3><p>
-<span class="apii">[-?, +?, &ndash;]</span>
-<pre>int lua_yield (lua_State *L, int nresults);</pre>
-<p>
-This function is equivalent to <a href="#lua_yieldk"><code>lua_yieldk</code></a>,
-but it has no continuation (see <a href="#4.7">&sect;4.7</a>).
-Therefore, when the thread resumes,
-it returns to the function that called
-the function calling <code>lua_yield</code>.
-<hr><h3><a name="lua_yieldk"><code>lua_yieldk</code></a></h3><p>
-<span class="apii">[-?, +?, &ndash;]</span>
-<pre>int lua_yieldk (lua_State *L, int nresults, int ctx, lua_CFunction k);</pre>
-<p>
-Yields a coroutine.
-<p>
-This function should only be called as the
-return expression of a C&nbsp;function, as follows:
-<pre>
-return lua_yieldk (L, n, i, k);
-</pre><p>
-When a C&nbsp;function calls <a href="#lua_yieldk"><code>lua_yieldk</code></a> in that way,
-the running coroutine suspends its execution,
-and the call to <a href="#lua_resume"><code>lua_resume</code></a> that started this coroutine returns.
-The parameter <code>nresults</code> is the number of values from the stack
-that are passed as results to <a href="#lua_resume"><code>lua_resume</code></a>.
-<p>
-When the coroutine is resumed again,
-Lua calls the given continuation function <code>k</code> to continue
-the execution of the C function that yielded (see <a href="#4.7">&sect;4.7</a>).
-This continuation function receives the same stack
-from the previous function,
-with the results removed and
-replaced by the arguments passed to <a href="#lua_resume"><code>lua_resume</code></a>.
-Moreover,
-the continuation function may access the value <code>ctx</code>
-by calling <a href="#lua_getctx"><code>lua_getctx</code></a>.
-<h2>4.9 &ndash; <a name="4.9">The Debug Interface</a></h2>
-<p>
-Lua has no built-in debugging facilities.
-Instead, it offers a special interface
-by means of functions and <em>hooks</em>.
-This interface allows the construction of different
-kinds of debuggers, profilers, and other tools
-that need "inside information" from the interpreter.
-<hr><h3><a name="lua_Debug"><code>lua_Debug</code></a></h3>
-<pre>typedef struct lua_Debug {
-int event;
-const char *name;           /* (n) */
-const char *namewhat;       /* (n) */
-const char *what;           /* (S) */
-const char *source;         /* (S) */
-int currentline;            /* (l) */
-int linedefined;            /* (S) */
-int lastlinedefined;        /* (S) */
-unsigned char nups;         /* (u) number of upvalues */
-unsigned char nparams;      /* (u) number of parameters */
-char isvararg;              /* (u) */
-char istailcall;            /* (t) */
-char short_src[LUA_IDSIZE]; /* (S) */
-/* private part */
-<em>other fields</em>
-} lua_Debug;</pre>
-<p>
-A structure used to carry different pieces of
-information about a function or an activation record.
-<a href="#lua_getstack"><code>lua_getstack</code></a> fills only the private part
-of this structure, for later use.
-To fill the other fields of <a href="#lua_Debug"><code>lua_Debug</code></a> with useful information,
-call <a href="#lua_getinfo"><code>lua_getinfo</code></a>.
-<p>
-The fields of <a href="#lua_Debug"><code>lua_Debug</code></a> have the following meaning:
-<ul>
-<li><b><code>source</code>: </b>
-the source of the chunk that created the function.
-If <code>source</code> starts with a '<code>@</code>',
-it means that the function was defined in a file where
-the file name follows the '<code>@</code>'.
-If <code>source</code> starts with a '<code>=</code>',
-the remainder of its contents describe the source in a user-dependent manner.
-Otherwise,
-the function was defined in a string where
-<code>source</code> is that string.
-</li>
-<li><b><code>short_src</code>: </b>
-a "printable" version of <code>source</code>, to be used in error messages.
-</li>
-<li><b><code>linedefined</code>: </b>
-the line number where the definition of the function starts.
-</li>
-<li><b><code>lastlinedefined</code>: </b>
-the line number where the definition of the function ends.
-</li>
-<li><b><code>what</code>: </b>
-the string <code>"Lua"</code> if the function is a Lua function,
-<code>"C"</code> if it is a C&nbsp;function,
-<code>"main"</code> if it is the main part of a chunk.
-</li>
-<li><b><code>currentline</code>: </b>
-the current line where the given function is executing.
-When no line information is available,
-<code>currentline</code> is set to -1.
-</li>
-<li><b><code>name</code>: </b>
-a reasonable name for the given function.
-Because functions in Lua are first-class values,
-they do not have a fixed name:
-some functions can be the value of multiple global variables,
-while others can be stored only in a table field.
-The <code>lua_getinfo</code> function checks how the function was
-called to find a suitable name.
-If it cannot find a name,
-then <code>name</code> is set to <code>NULL</code>.
-</li>
-<li><b><code>namewhat</code>: </b>
-explains the <code>name</code> field.
-The value of <code>namewhat</code> can be
-<code>"global"</code>, <code>"local"</code>, <code>"method"</code>,
-<code>"field"</code>, <code>"upvalue"</code>, or <code>""</code> (the empty string),
-according to how the function was called.
-(Lua uses the empty string when no other option seems to apply.)
-</li>
-<li><b><code>istailcall</code>: </b>
-true if this function invocation was called by a tail call.
-In this case, the caller of this level is not in the stack.
-</li>
-<li><b><code>nups</code>: </b>
-the number of upvalues of the function.
-</li>
-<li><b><code>nparams</code>: </b>
-the number of fixed parameters of the function
-(always 0&nbsp;for C&nbsp;functions).
-</li>
-<li><b><code>isvararg</code>: </b>
-true if the function is a vararg function
-(always true for C&nbsp;functions).
-</li>
-</ul>
-<hr><h3><a name="lua_gethook"><code>lua_gethook</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_Hook lua_gethook (lua_State *L);</pre>
-<p>
-Returns the current hook function.
-<hr><h3><a name="lua_gethookcount"><code>lua_gethookcount</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_gethookcount (lua_State *L);</pre>
-<p>
-Returns the current hook count.
-<hr><h3><a name="lua_gethookmask"><code>lua_gethookmask</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_gethookmask (lua_State *L);</pre>
-<p>
-Returns the current hook mask.
-<hr><h3><a name="lua_getinfo"><code>lua_getinfo</code></a></h3><p>
-<span class="apii">[-(0|1), +(0|1|2), <em>e</em>]</span>
-<pre>int lua_getinfo (lua_State *L, const char *what, lua_Debug *ar);</pre>
-<p>
-Gets information about a specific function or function invocation.
-<p>
-To get information about a function invocation,
-the parameter <code>ar</code> must be a valid activation record that was
-filled by a previous call to <a href="#lua_getstack"><code>lua_getstack</code></a> or
-given as argument to a hook (see <a href="#lua_Hook"><code>lua_Hook</code></a>).
-<p>
-To get information about a function you push it onto the stack
-and start the <code>what</code> string with the character '<code>&gt;</code>'.
-(In that case,
-<code>lua_getinfo</code> pops the function from the top of the stack.)
-For instance, to know in which line a function <code>f</code> was defined,
-you can write the following code:
-<pre>
-lua_Debug ar;
-lua_getglobal(L, "f");  /* get global 'f' */
-lua_getinfo(L, "&gt;S", &amp;ar);
-printf("%d\n", ar.linedefined);
-</pre>
-<p>
-Each character in the string <code>what</code>
-selects some fields of the structure <code>ar</code> to be filled or
-a value to be pushed on the stack:
-<ul>
-<li><b>'<code>n</code>': </b> fills in the field <code>name</code> and <code>namewhat</code>;
-</li>
-<li><b>'<code>S</code>': </b>
-fills in the fields <code>source</code>, <code>short_src</code>,
-<code>linedefined</code>, <code>lastlinedefined</code>, and <code>what</code>;
-</li>
-<li><b>'<code>l</code>': </b> fills in the field <code>currentline</code>;
-</li>
-<li><b>'<code>t</code>': </b> fills in the field <code>istailcall</code>;
-</li>
-<li><b>'<code>u</code>': </b> fills in the fields
-<code>nups</code>, <code>nparams</code>, and <code>isvararg</code>;
-</li>
-<li><b>'<code>f</code>': </b>
-pushes onto the stack the function that is
-running at the given level;
-</li>
-<li><b>'<code>L</code>': </b>
-pushes onto the stack a table whose indices are the
-numbers of the lines that are valid on the function.
-(A <em>valid line</em> is a line with some associated code,
-that is, a line where you can put a break point.
-Non-valid lines include empty lines and comments.)
-</li>
-</ul>
-<p>
-This function returns 0 on error
-(for instance, an invalid option in <code>what</code>).
-<hr><h3><a name="lua_getlocal"><code>lua_getlocal</code></a></h3><p>
-<span class="apii">[-0, +(0|1), &ndash;]</span>
-<pre>const char *lua_getlocal (lua_State *L, lua_Debug *ar, int n);</pre>
-<p>
-Gets information about a local variable of
-a given activation record or a given function.
-<p>
-In the first case,
-the parameter <code>ar</code> must be a valid activation record that was
-filled by a previous call to <a href="#lua_getstack"><code>lua_getstack</code></a> or
-given as argument to a hook (see <a href="#lua_Hook"><code>lua_Hook</code></a>).
-The index <code>n</code> selects which local variable to inspect;
-see <a href="#pdf-debug.getlocal"><code>debug.getlocal</code></a> for details about variable indices
-and names.
-<p>
-<a href="#lua_getlocal"><code>lua_getlocal</code></a> pushes the variable's value onto the stack
-and returns its name.
-<p>
-In the second case, <code>ar</code> should be <code>NULL</code> and the function
-to be inspected must be at the top of the stack.
-In this case, only parameters of Lua functions are visible
-(as there is no information about what variables are active)
-and no values are pushed onto the stack.
-<p>
-Returns <code>NULL</code> (and pushes nothing)
-when the index is greater than
-the number of active local variables.
-<hr><h3><a name="lua_getstack"><code>lua_getstack</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_getstack (lua_State *L, int level, lua_Debug *ar);</pre>
-<p>
-Gets information about the interpreter runtime stack.
-<p>
-This function fills parts of a <a href="#lua_Debug"><code>lua_Debug</code></a> structure with
-an identification of the <em>activation record</em>
-of the function executing at a given level.
-Level&nbsp;0 is the current running function,
-whereas level <em>n+1</em> is the function that has called level <em>n</em>
-(except for tail calls, which do not count on the stack).
-When there are no errors, <a href="#lua_getstack"><code>lua_getstack</code></a> returns 1;
-when called with a level greater than the stack depth,
-it returns 0.
-<hr><h3><a name="lua_getupvalue"><code>lua_getupvalue</code></a></h3><p>
-<span class="apii">[-0, +(0|1), &ndash;]</span>
-<pre>const char *lua_getupvalue (lua_State *L, int funcindex, int n);</pre>
-<p>
-Gets information about a closure's upvalue.
-(For Lua functions,
-upvalues are the external local variables that the function uses,
-and that are consequently included in its closure.)
-<a href="#lua_getupvalue"><code>lua_getupvalue</code></a> gets the index <code>n</code> of an upvalue,
-pushes the upvalue's value onto the stack,
-and returns its name.
-<code>funcindex</code> points to the closure in the stack.
-(Upvalues have no particular order,
-as they are active through the whole function.
-So, they are numbered in an arbitrary order.)
-<p>
-Returns <code>NULL</code> (and pushes nothing)
-when the index is greater than the number of upvalues.
-For C&nbsp;functions, this function uses the empty string <code>""</code>
-as a name for all upvalues.
-<hr><h3><a name="lua_Hook"><code>lua_Hook</code></a></h3>
-<pre>typedef void (*lua_Hook) (lua_State *L, lua_Debug *ar);</pre>
-<p>
-Type for debugging hook functions.
-<p>
-Whenever a hook is called, its <code>ar</code> argument has its field
-<code>event</code> set to the specific event that triggered the hook.
-Lua identifies these events with the following constants:
-<a name="pdf-LUA_HOOKCALL"><code>LUA_HOOKCALL</code></a>, <a name="pdf-LUA_HOOKRET"><code>LUA_HOOKRET</code></a>,
-<a name="pdf-LUA_HOOKTAILCALL"><code>LUA_HOOKTAILCALL</code></a>, <a name="pdf-LUA_HOOKLINE"><code>LUA_HOOKLINE</code></a>,
-and <a name="pdf-LUA_HOOKCOUNT"><code>LUA_HOOKCOUNT</code></a>.
-Moreover, for line events, the field <code>currentline</code> is also set.
-To get the value of any other field in <code>ar</code>,
-the hook must call <a href="#lua_getinfo"><code>lua_getinfo</code></a>.
-<p>
-For call events, <code>event</code> can be <code>LUA_HOOKCALL</code>,
-the normal value, or <code>LUA_HOOKTAILCALL</code>, for a tail call;
-in this case, there will be no corresponding return event.
-<p>
-While Lua is running a hook, it disables other calls to hooks.
-Therefore, if a hook calls back Lua to execute a function or a chunk,
-this execution occurs without any calls to hooks.
-<p>
-Hook functions cannot have continuations,
-that is, they cannot call <a href="#lua_yieldk"><code>lua_yieldk</code></a>,
-<a href="#lua_pcallk"><code>lua_pcallk</code></a>, or <a href="#lua_callk"><code>lua_callk</code></a> with a non-null <code>k</code>.
-<p>
-Hook functions can yield under the following conditions:
-Only count and line events can yield
-and they cannot yield any value;
-to yield a hook function must finish its execution
-calling <a href="#lua_yield"><code>lua_yield</code></a> with <code>nresults</code> equal to zero.
-<hr><h3><a name="lua_sethook"><code>lua_sethook</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_sethook (lua_State *L, lua_Hook f, int mask, int count);</pre>
-<p>
-Sets the debugging hook function.
-<p>
-Argument <code>f</code> is the hook function.
-<code>mask</code> specifies on which events the hook will be called:
-it is formed by a bitwise or of the constants
-<a name="pdf-LUA_MASKCALL"><code>LUA_MASKCALL</code></a>,
-<a name="pdf-LUA_MASKRET"><code>LUA_MASKRET</code></a>,
-<a name="pdf-LUA_MASKLINE"><code>LUA_MASKLINE</code></a>,
-and <a name="pdf-LUA_MASKCOUNT"><code>LUA_MASKCOUNT</code></a>.
-The <code>count</code> argument is only meaningful when the mask
-includes <code>LUA_MASKCOUNT</code>.
-For each event, the hook is called as explained below:
-<ul>
-<li><b>The call hook: </b> is called when the interpreter calls a function.
-The hook is called just after Lua enters the new function,
-before the function gets its arguments.
-</li>
-<li><b>The return hook: </b> is called when the interpreter returns from a function.
-The hook is called just before Lua leaves the function.
-There is no standard way to access the values
-to be returned by the function.
-</li>
-<li><b>The line hook: </b> is called when the interpreter is about to
-start the execution of a new line of code,
-or when it jumps back in the code (even to the same line).
-(This event only happens while Lua is executing a Lua function.)
-</li>
-<li><b>The count hook: </b> is called after the interpreter executes every
-<code>count</code> instructions.
-(This event only happens while Lua is executing a Lua function.)
-</li>
-</ul>
-<p>
-A hook is disabled by setting <code>mask</code> to zero.
-<hr><h3><a name="lua_setlocal"><code>lua_setlocal</code></a></h3><p>
-<span class="apii">[-(0|1), +0, &ndash;]</span>
-<pre>const char *lua_setlocal (lua_State *L, lua_Debug *ar, int n);</pre>
-<p>
-Sets the value of a local variable of a given activation record.
-Parameters <code>ar</code> and <code>n</code> are as in <a href="#lua_getlocal"><code>lua_getlocal</code></a>
-(see <a href="#lua_getlocal"><code>lua_getlocal</code></a>).
-<a href="#lua_setlocal"><code>lua_setlocal</code></a> assigns the value at the top of the stack
-to the variable and returns its name.
-It also pops the value from the stack.
-<p>
-Returns <code>NULL</code> (and pops nothing)
-when the index is greater than
-the number of active local variables.
-<hr><h3><a name="lua_setupvalue"><code>lua_setupvalue</code></a></h3><p>
-<span class="apii">[-(0|1), +0, &ndash;]</span>
-<pre>const char *lua_setupvalue (lua_State *L, int funcindex, int n);</pre>
-<p>
-Sets the value of a closure's upvalue.
-It assigns the value at the top of the stack
-to the upvalue and returns its name.
-It also pops the value from the stack.
-Parameters <code>funcindex</code> and <code>n</code> are as in the <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>
-(see <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>).
-<p>
-Returns <code>NULL</code> (and pops nothing)
-when the index is greater than the number of upvalues.
-<hr><h3><a name="lua_upvalueid"><code>lua_upvalueid</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void *lua_upvalueid (lua_State *L, int funcindex, int n);</pre>
-<p>
-Returns an unique identifier for the upvalue numbered <code>n</code>
-from the closure at index <code>funcindex</code>.
-Parameters <code>funcindex</code> and <code>n</code> are as in the <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>
-(see <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>)
-(but <code>n</code> cannot be greater than the number of upvalues).
-<p>
-These unique identifiers allow a program to check whether different
-closures share upvalues.
-Lua closures that share an upvalue
-(that is, that access a same external local variable)
-will return identical ids for those upvalue indices.
-<hr><h3><a name="lua_upvaluejoin"><code>lua_upvaluejoin</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void lua_upvaluejoin (lua_State *L, int funcindex1, int n1,
-int funcindex2, int n2);</pre>
-<p>
-Make the <code>n1</code>-th upvalue of the Lua closure at index <code>funcindex1</code>
-refer to the <code>n2</code>-th upvalue of the Lua closure at index <code>funcindex2</code>.
 <h1>5 &ndash; <a name="5">The Auxiliary Library</a></h1>
 <p>
+Like the previous section, this section is specific to Lua and is not relevant to Luan.
-The <em>auxiliary library</em> provides several convenient functions
+So this section is just a placeholder.
-to interface C with Lua.
-While the basic API provides the primitive functions for all
-interactions between C and Lua,
-the auxiliary library provides higher-level functions for some
-common tasks.
-<p>
-All functions and types from the auxiliary library
-are defined in header file <code>lauxlib.h</code> and
-have a prefix <code>luaL_</code>.
-<p>
-All functions in the auxiliary library are built on
-top of the basic API,
-and so they provide nothing that cannot be done with that API.
-Nevertheless, the use of the auxiliary library ensures
-more consistency to your code.
-<p>
-Several functions in the auxiliary library use internally some
-extra stack slots.
-When a function in the auxiliary library uses less than five slots,
-it does not check the stack size;
-it simply assumes that there are enough slots.
-<p>
-Several functions in the auxiliary library are used to
-check C&nbsp;function arguments.
-Because the error message is formatted for arguments
-(e.g., "<code>bad argument #1</code>"),
-you should not use these functions for other stack values.
-<p>
-Functions called <code>luaL_check*</code>
-always throw an error if the check is not satisfied.
-<h2>5.1 &ndash; <a name="5.1">Functions and Types</a></h2>
-<p>
-Here we list all functions and types from the auxiliary library
-in alphabetical order.
-<hr><h3><a name="luaL_addchar"><code>luaL_addchar</code></a></h3><p>
-<span class="apii">[-?, +?, <em>e</em>]</span>
-<pre>void luaL_addchar (luaL_Buffer *B, char c);</pre>
-<p>
-Adds the byte <code>c</code> to the buffer <code>B</code>
-(see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
-<hr><h3><a name="luaL_addlstring"><code>luaL_addlstring</code></a></h3><p>
-<span class="apii">[-?, +?, <em>e</em>]</span>
-<pre>void luaL_addlstring (luaL_Buffer *B, const char *s, size_t l);</pre>
-<p>
-Adds the string pointed to by <code>s</code> with length <code>l</code> to
-the buffer <code>B</code>
-(see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
-The string can contain embedded zeros.
-<hr><h3><a name="luaL_addsize"><code>luaL_addsize</code></a></h3><p>
-<span class="apii">[-?, +?, <em>e</em>]</span>
-<pre>void luaL_addsize (luaL_Buffer *B, size_t n);</pre>
-<p>
-Adds to the buffer <code>B</code> (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>)
-a string of length <code>n</code> previously copied to the
-buffer area (see <a href="#luaL_prepbuffer"><code>luaL_prepbuffer</code></a>).
-<hr><h3><a name="luaL_addstring"><code>luaL_addstring</code></a></h3><p>
-<span class="apii">[-?, +?, <em>e</em>]</span>
-<pre>void luaL_addstring (luaL_Buffer *B, const char *s);</pre>
-<p>
-Adds the zero-terminated string pointed to by <code>s</code>
-to the buffer <code>B</code>
-(see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
-The string cannot contain embedded zeros.
-<hr><h3><a name="luaL_addvalue"><code>luaL_addvalue</code></a></h3><p>
-<span class="apii">[-1, +?, <em>e</em>]</span>
-<pre>void luaL_addvalue (luaL_Buffer *B);</pre>
-<p>
-Adds the value at the top of the stack
-to the buffer <code>B</code>
-(see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
-Pops the value.
-<p>
-This is the only function on string buffers that can (and must)
-be called with an extra element on the stack,
-which is the value to be added to the buffer.
-<hr><h3><a name="luaL_argcheck"><code>luaL_argcheck</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>void luaL_argcheck (lua_State *L,
-int cond,
-int arg,
-const char *extramsg);</pre>
-<p>
-Checks whether <code>cond</code> is true.
-If not, raises an error with a standard message.
-<hr><h3><a name="luaL_argerror"><code>luaL_argerror</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>int luaL_argerror (lua_State *L, int arg, const char *extramsg);</pre>
-<p>
-Raises an error with a standard message
-that includes <code>extramsg</code> as a comment.
-<p>
-This function never returns,
-but it is an idiom to use it in C&nbsp;functions
-as <code>return luaL_argerror(<em>args</em>)</code>.
-<hr><h3><a name="luaL_Buffer"><code>luaL_Buffer</code></a></h3>
-<pre>typedef struct luaL_Buffer luaL_Buffer;</pre>
-<p>
-Type for a <em>string buffer</em>.
-<p>
-A string buffer allows C&nbsp;code to build Lua strings piecemeal.
-Its pattern of use is as follows:
-<ul>
-<li>First declare a variable <code>b</code> of type <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>.</li>
-<li>Then initialize it with a call <code>luaL_buffinit(L, &amp;b)</code>.</li>
-<li>
-Then add string pieces to the buffer calling any of
-the <code>luaL_add*</code> functions.
-</li>
-<li>
-Finish by calling <code>luaL_pushresult(&amp;b)</code>.
-This call leaves the final string on the top of the stack.
-</li>
-</ul>
-<p>
-If you know beforehand the total size of the resulting string,
-you can use the buffer like this:
-<ul>
-<li>First declare a variable <code>b</code> of type <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>.</li>
-<li>Then initialize it and preallocate a space of
-size <code>sz</code> with a call <code>luaL_buffinitsize(L, &amp;b, sz)</code>.</li>
-<li>Then copy the string into that space.</li>
-<li>
-Finish by calling <code>luaL_pushresultsize(&amp;b, sz)</code>,
-where <code>sz</code> is the total size of the resulting string
-copied into that space.
-</li>
-</ul>
-<p>
-During its normal operation,
-a string buffer uses a variable number of stack slots.
-So, while using a buffer, you cannot assume that you know where
-the top of the stack is.
-You can use the stack between successive calls to buffer operations
-as long as that use is balanced;
-that is,
-when you call a buffer operation,
-the stack is at the same level
-it was immediately after the previous buffer operation.
-(The only exception to this rule is <a href="#luaL_addvalue"><code>luaL_addvalue</code></a>.)
-After calling <a href="#luaL_pushresult"><code>luaL_pushresult</code></a> the stack is back to its
-level when the buffer was initialized,
-plus the final string on its top.
-<hr><h3><a name="luaL_buffinit"><code>luaL_buffinit</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void luaL_buffinit (lua_State *L, luaL_Buffer *B);</pre>
-<p>
-Initializes a buffer <code>B</code>.
-This function does not allocate any space;
-the buffer must be declared as a variable
-(see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
-<hr><h3><a name="luaL_buffinitsize"><code>luaL_buffinitsize</code></a></h3><p>
-<span class="apii">[-?, +?, <em>e</em>]</span>
-<pre>char *luaL_buffinitsize (lua_State *L, luaL_Buffer *B, size_t sz);</pre>
-<p>
-Equivalent to the sequence
-<a href="#luaL_buffinit"><code>luaL_buffinit</code></a>, <a href="#luaL_prepbuffsize"><code>luaL_prepbuffsize</code></a>.
-<hr><h3><a name="luaL_callmeta"><code>luaL_callmeta</code></a></h3><p>
-<span class="apii">[-0, +(0|1), <em>e</em>]</span>
-<pre>int luaL_callmeta (lua_State *L, int obj, const char *e);</pre>
-<p>
-Calls a metamethod.
-<p>
-If the object at index <code>obj</code> has a metatable and this
-metatable has a field <code>e</code>,
-this function calls this field passing the object as its only argument.
-In this case this function returns true and pushes onto the
-stack the value returned by the call.
-If there is no metatable or no metamethod,
-this function returns false (without pushing any value on the stack).
-<hr><h3><a name="luaL_checkany"><code>luaL_checkany</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>void luaL_checkany (lua_State *L, int arg);</pre>
-<p>
-Checks whether the function has an argument
-of any type (including <b>nil</b>) at position <code>arg</code>.
-<hr><h3><a name="luaL_checkint"><code>luaL_checkint</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>int luaL_checkint (lua_State *L, int arg);</pre>
-<p>
-Checks whether the function argument <code>arg</code> is a number
-and returns this number cast to an <code>int</code>.
-<hr><h3><a name="luaL_checkinteger"><code>luaL_checkinteger</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>lua_Integer luaL_checkinteger (lua_State *L, int arg);</pre>
-<p>
-Checks whether the function argument <code>arg</code> is a number
-and returns this number cast to a <a href="#lua_Integer"><code>lua_Integer</code></a>.
-<hr><h3><a name="luaL_checklong"><code>luaL_checklong</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>long luaL_checklong (lua_State *L, int arg);</pre>
-<p>
-Checks whether the function argument <code>arg</code> is a number
-and returns this number cast to a <code>long</code>.
-<hr><h3><a name="luaL_checklstring"><code>luaL_checklstring</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>const char *luaL_checklstring (lua_State *L, int arg, size_t *l);</pre>
-<p>
-Checks whether the function argument <code>arg</code> is a string
-and returns this string;
-if <code>l</code> is not <code>NULL</code> fills <code>*l</code>
-with the string's length.
-<p>
-This function uses <a href="#lua_tolstring"><code>lua_tolstring</code></a> to get its result,
-so all conversions and caveats of that function apply here.
-<hr><h3><a name="luaL_checknumber"><code>luaL_checknumber</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>lua_Number luaL_checknumber (lua_State *L, int arg);</pre>
-<p>
-Checks whether the function argument <code>arg</code> is a number
-and returns this number.
-<hr><h3><a name="luaL_checkoption"><code>luaL_checkoption</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>int luaL_checkoption (lua_State *L,
-int arg,
-const char *def,
-const char *const lst[]);</pre>
-<p>
-Checks whether the function argument <code>arg</code> is a string and
-searches for this string in the array <code>lst</code>
-(which must be NULL-terminated).
-Returns the index in the array where the string was found.
-Raises an error if the argument is not a string or
-if the string cannot be found.
-<p>
-If <code>def</code> is not <code>NULL</code>,
-the function uses <code>def</code> as a default value when
-there is no argument <code>arg</code> or when this argument is <b>nil</b>.
-<p>
-This is a useful function for mapping strings to C&nbsp;enums.
-(The usual convention in Lua libraries is
-to use strings instead of numbers to select options.)
-<hr><h3><a name="luaL_checkstack"><code>luaL_checkstack</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>void luaL_checkstack (lua_State *L, int sz, const char *msg);</pre>
-<p>
-Grows the stack size to <code>top + sz</code> elements,
-raising an error if the stack cannot grow to that size.
-<code>msg</code> is an additional text to go into the error message
-(or <code>NULL</code> for no additional text).
-<hr><h3><a name="luaL_checkstring"><code>luaL_checkstring</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>const char *luaL_checkstring (lua_State *L, int arg);</pre>
-<p>
-Checks whether the function argument <code>arg</code> is a string
-and returns this string.
-<p>
-This function uses <a href="#lua_tolstring"><code>lua_tolstring</code></a> to get its result,
-so all conversions and caveats of that function apply here.
-<hr><h3><a name="luaL_checktype"><code>luaL_checktype</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>void luaL_checktype (lua_State *L, int arg, int t);</pre>
-<p>
-Checks whether the function argument <code>arg</code> has type <code>t</code>.
-See <a href="#lua_type"><code>lua_type</code></a> for the encoding of types for <code>t</code>.
-<hr><h3><a name="luaL_checkudata"><code>luaL_checkudata</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>void *luaL_checkudata (lua_State *L, int arg, const char *tname);</pre>
-<p>
-Checks whether the function argument <code>arg</code> is a userdata
-of the type <code>tname</code> (see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code></a>) and
-returns the userdata address (see <a href="#lua_touserdata"><code>lua_touserdata</code></a>).
-<hr><h3><a name="luaL_checkunsigned"><code>luaL_checkunsigned</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>lua_Unsigned luaL_checkunsigned (lua_State *L, int arg);</pre>
-<p>
-Checks whether the function argument <code>arg</code> is a number
-and returns this number cast to a <a href="#lua_Unsigned"><code>lua_Unsigned</code></a>.
-<hr><h3><a name="luaL_checkversion"><code>luaL_checkversion</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void luaL_checkversion (lua_State *L);</pre>
-<p>
-Checks whether the core running the call,
-the core that created the Lua state,
-and the code making the call are all using the same version of Lua.
-Also checks whether the core running the call
-and the core that created the Lua state
-are using the same address space.
-<hr><h3><a name="luaL_dofile"><code>luaL_dofile</code></a></h3><p>
-<span class="apii">[-0, +?, <em>e</em>]</span>
-<pre>int luaL_dofile (lua_State *L, const char *filename);</pre>
-<p>
-Loads and runs the given file.
-It is defined as the following macro:
-<pre>
-(luaL_loadfile(L, filename) || lua_pcall(L, 0, LUA_MULTRET, 0))
-</pre><p>
-It returns false if there are no errors
-or true in case of errors.
-<hr><h3><a name="luaL_dostring"><code>luaL_dostring</code></a></h3><p>
-<span class="apii">[-0, +?, &ndash;]</span>
-<pre>int luaL_dostring (lua_State *L, const char *str);</pre>
-<p>
-Loads and runs the given string.
-It is defined as the following macro:
-<pre>
-(luaL_loadstring(L, str) || lua_pcall(L, 0, LUA_MULTRET, 0))
-</pre><p>
-It returns false if there are no errors
-or true in case of errors.
-<hr><h3><a name="luaL_error"><code>luaL_error</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>int luaL_error (lua_State *L, const char *fmt, ...);</pre>
-<p>
-Raises an error.
-The error message format is given by <code>fmt</code>
-plus any extra arguments,
-following the same rules of <a href="#lua_pushfstring"><code>lua_pushfstring</code></a>.
-It also adds at the beginning of the message the file name and
-the line number where the error occurred,
-if this information is available.
-<p>
-This function never returns,
-but it is an idiom to use it in C&nbsp;functions
-as <code>return luaL_error(<em>args</em>)</code>.
-<hr><h3><a name="luaL_execresult"><code>luaL_execresult</code></a></h3><p>
-<span class="apii">[-0, +3, <em>e</em>]</span>
-<pre>int luaL_execresult (lua_State *L, int stat);</pre>
-<p>
-This function produces the return values for
-process-related functions in the standard library
-(<a href="#pdf-os.execute"><code>os.execute</code></a> and <a href="#pdf-io.close"><code>io.close</code></a>).
-<hr><h3><a name="luaL_fileresult"><code>luaL_fileresult</code></a></h3><p>
-<span class="apii">[-0, +(1|3), <em>e</em>]</span>
-<pre>int luaL_fileresult (lua_State *L, int stat, const char *fname);</pre>
-<p>
-This function produces the return values for
-file-related functions in the standard library
-(<a href="#pdf-io.open"><code>io.open</code></a>, <a href="#pdf-os.rename"><code>os.rename</code></a>, <a href="#pdf-file:seek"><code>file:seek</code></a>, etc.).
-<hr><h3><a name="luaL_getmetafield"><code>luaL_getmetafield</code></a></h3><p>
-<span class="apii">[-0, +(0|1), <em>e</em>]</span>
-<pre>int luaL_getmetafield (lua_State *L, int obj, const char *e);</pre>
-<p>
-Pushes onto the stack the field <code>e</code> from the metatable
-of the object at index <code>obj</code>.
-If the object does not have a metatable,
-or if the metatable does not have this field,
-returns false and pushes nothing.
-<hr><h3><a name="luaL_getmetatable"><code>luaL_getmetatable</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void luaL_getmetatable (lua_State *L, const char *tname);</pre>
-<p>
-Pushes onto the stack the metatable associated with name <code>tname</code>
-in the registry (see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code></a>).
-<hr><h3><a name="luaL_getsubtable"><code>luaL_getsubtable</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>int luaL_getsubtable (lua_State *L, int idx, const char *fname);</pre>
-<p>
-Ensures that the value <code>t[fname]</code>,
-where <code>t</code> is the value at index <code>idx</code>,
-is a table,
-and pushes that table onto the stack.
-Returns true if it finds a previous table there
-and false if it creates a new table.
-<hr><h3><a name="luaL_gsub"><code>luaL_gsub</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>const char *luaL_gsub (lua_State *L,
-const char *s,
-const char *p,
-const char *r);</pre>
-<p>
-Creates a copy of string <code>s</code> by replacing
-any occurrence of the string <code>p</code>
-with the string <code>r</code>.
-Pushes the resulting string on the stack and returns it.
-<hr><h3><a name="luaL_len"><code>luaL_len</code></a></h3><p>
-<span class="apii">[-0, +0, <em>e</em>]</span>
-<pre>int luaL_len (lua_State *L, int index);</pre>
-<p>
-Returns the "length" of the value at the given index
-as a number;
-it is equivalent to the '<code>#</code>' operator in Lua (see <a href="#3.4.6">&sect;3.4.6</a>).
-Raises an error if the result of the operation is not a number.
-(This case only can happen through metamethods.)
-<hr><h3><a name="luaL_loadbuffer"><code>luaL_loadbuffer</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>int luaL_loadbuffer (lua_State *L,
-const char *buff,
-size_t sz,
-const char *name);</pre>
-<p>
-Equivalent to <a href="#luaL_loadbufferx"><code>luaL_loadbufferx</code></a> with <code>mode</code> equal to <code>NULL</code>.
-<hr><h3><a name="luaL_loadbufferx"><code>luaL_loadbufferx</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>int luaL_loadbufferx (lua_State *L,
-const char *buff,
-size_t sz,
-const char *name,
-const char *mode);</pre>
-<p>
-Loads a buffer as a Lua chunk.
-This function uses <a href="#lua_load"><code>lua_load</code></a> to load the chunk in the
-buffer pointed to by <code>buff</code> with size <code>sz</code>.
-<p>
-This function returns the same results as <a href="#lua_load"><code>lua_load</code></a>.
-<code>name</code> is the chunk name,
-used for debug information and error messages.
-The string <code>mode</code> works as in function <a href="#lua_load"><code>lua_load</code></a>.
-<hr><h3><a name="luaL_loadfile"><code>luaL_loadfile</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>int luaL_loadfile (lua_State *L, const char *filename);</pre>
-<p>
-Equivalent to <a href="#luaL_loadfilex"><code>luaL_loadfilex</code></a> with <code>mode</code> equal to <code>NULL</code>.
-<hr><h3><a name="luaL_loadfilex"><code>luaL_loadfilex</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>int luaL_loadfilex (lua_State *L, const char *filename,
-const char *mode);</pre>
-<p>
-Loads a file as a Lua chunk.
-This function uses <a href="#lua_load"><code>lua_load</code></a> to load the chunk in the file
-named <code>filename</code>.
-If <code>filename</code> is <code>NULL</code>,
-then it loads from the standard input.
-The first line in the file is ignored if it starts with a <code>#</code>.
-<p>
-The string <code>mode</code> works as in function <a href="#lua_load"><code>lua_load</code></a>.
-<p>
-This function returns the same results as <a href="#lua_load"><code>lua_load</code></a>,
-but it has an extra error code <a name="pdf-LUA_ERRFILE"><code>LUA_ERRFILE</code></a>
-if it cannot open/read the file or the file has a wrong mode.
-<p>
-As <a href="#lua_load"><code>lua_load</code></a>, this function only loads the chunk;
-it does not run it.
-<hr><h3><a name="luaL_loadstring"><code>luaL_loadstring</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>int luaL_loadstring (lua_State *L, const char *s);</pre>
-<p>
-Loads a string as a Lua chunk.
-This function uses <a href="#lua_load"><code>lua_load</code></a> to load the chunk in
-the zero-terminated string <code>s</code>.
-<p>
-This function returns the same results as <a href="#lua_load"><code>lua_load</code></a>.
-<p>
-Also as <a href="#lua_load"><code>lua_load</code></a>, this function only loads the chunk;
-it does not run it.
-<hr><h3><a name="luaL_newlib"><code>luaL_newlib</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void luaL_newlib (lua_State *L, const luaL_Reg *l);</pre>
-<p>
-Creates a new table and registers there
-the functions in list <code>l</code>.
-It is implemented as the following macro:
-<pre>
-(luaL_newlibtable(L,l), luaL_setfuncs(L,l,0))
-</pre>
-<hr><h3><a name="luaL_newlibtable"><code>luaL_newlibtable</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void luaL_newlibtable (lua_State *L, const luaL_Reg l[]);</pre>
-<p>
-Creates a new table with a size optimized
-to store all entries in the array <code>l</code>
-(but does not actually store them).
-It is intended to be used in conjunction with <a href="#luaL_setfuncs"><code>luaL_setfuncs</code></a>
-(see <a href="#luaL_newlib"><code>luaL_newlib</code></a>).
-<p>
-It is implemented as a macro.
-The array <code>l</code> must be the actual array,
-not a pointer to it.
-<hr><h3><a name="luaL_newmetatable"><code>luaL_newmetatable</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>int luaL_newmetatable (lua_State *L, const char *tname);</pre>
-<p>
-If the registry already has the key <code>tname</code>,
-returns 0.
-Otherwise,
-creates a new table to be used as a metatable for userdata,
-adds it to the registry with key <code>tname</code>,
-and returns 1.
-<p>
-In both cases pushes onto the stack the final value associated
-with <code>tname</code> in the registry.
-<hr><h3><a name="luaL_newstate"><code>luaL_newstate</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_State *luaL_newstate (void);</pre>
-<p>
-Creates a new Lua state.
-It calls <a href="#lua_newstate"><code>lua_newstate</code></a> with an
-allocator based on the standard&nbsp;C <code>realloc</code> function
-and then sets a panic function (see <a href="#4.6">&sect;4.6</a>) that prints
-an error message to the standard error output in case of fatal
-errors.
-<p>
-Returns the new state,
-or <code>NULL</code> if there is a memory allocation error.
-<hr><h3><a name="luaL_openlibs"><code>luaL_openlibs</code></a></h3><p>
-<span class="apii">[-0, +0, <em>e</em>]</span>
-<pre>void luaL_openlibs (lua_State *L);</pre>
-<p>
-Opens all standard Lua libraries into the given state.
-<hr><h3><a name="luaL_optint"><code>luaL_optint</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>int luaL_optint (lua_State *L, int arg, int d);</pre>
-<p>
-If the function argument <code>arg</code> is a number,
-returns this number cast to an <code>int</code>.
-If this argument is absent or is <b>nil</b>,
-returns <code>d</code>.
-Otherwise, raises an error.
-<hr><h3><a name="luaL_optinteger"><code>luaL_optinteger</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>lua_Integer luaL_optinteger (lua_State *L,
-int arg,
-lua_Integer d);</pre>
-<p>
-If the function argument <code>arg</code> is a number,
-returns this number cast to a <a href="#lua_Integer"><code>lua_Integer</code></a>.
-If this argument is absent or is <b>nil</b>,
-returns <code>d</code>.
-Otherwise, raises an error.
-<hr><h3><a name="luaL_optlong"><code>luaL_optlong</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>long luaL_optlong (lua_State *L, int arg, long d);</pre>
-<p>
-If the function argument <code>arg</code> is a number,
-returns this number cast to a <code>long</code>.
-If this argument is absent or is <b>nil</b>,
-returns <code>d</code>.
-Otherwise, raises an error.
-<hr><h3><a name="luaL_optlstring"><code>luaL_optlstring</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>const char *luaL_optlstring (lua_State *L,
-int arg,
-const char *d,
-size_t *l);</pre>
-<p>
-If the function argument <code>arg</code> is a string,
-returns this string.
-If this argument is absent or is <b>nil</b>,
-returns <code>d</code>.
-Otherwise, raises an error.
-<p>
-If <code>l</code> is not <code>NULL</code>,
-fills the position <code>*l</code> with the result's length.
-<hr><h3><a name="luaL_optnumber"><code>luaL_optnumber</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>lua_Number luaL_optnumber (lua_State *L, int arg, lua_Number d);</pre>
-<p>
-If the function argument <code>arg</code> is a number,
-returns this number.
-If this argument is absent or is <b>nil</b>,
-returns <code>d</code>.
-Otherwise, raises an error.
-<hr><h3><a name="luaL_optstring"><code>luaL_optstring</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>const char *luaL_optstring (lua_State *L,
-int arg,
-const char *d);</pre>
-<p>
-If the function argument <code>arg</code> is a string,
-returns this string.
-If this argument is absent or is <b>nil</b>,
-returns <code>d</code>.
-Otherwise, raises an error.
-<hr><h3><a name="luaL_optunsigned"><code>luaL_optunsigned</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>lua_Unsigned luaL_optunsigned (lua_State *L,
-int arg,
-lua_Unsigned u);</pre>
-<p>
-If the function argument <code>arg</code> is a number,
-returns this number cast to a <a href="#lua_Unsigned"><code>lua_Unsigned</code></a>.
-If this argument is absent or is <b>nil</b>,
-returns <code>u</code>.
-Otherwise, raises an error.
-<hr><h3><a name="luaL_prepbuffer"><code>luaL_prepbuffer</code></a></h3><p>
-<span class="apii">[-?, +?, <em>e</em>]</span>
-<pre>char *luaL_prepbuffer (luaL_Buffer *B);</pre>
-<p>
-Equivalent to <a href="#luaL_prepbuffsize"><code>luaL_prepbuffsize</code></a>
-with the predefined size <a name="pdf-LUAL_BUFFERSIZE"><code>LUAL_BUFFERSIZE</code></a>.
-<hr><h3><a name="luaL_prepbuffsize"><code>luaL_prepbuffsize</code></a></h3><p>
-<span class="apii">[-?, +?, <em>e</em>]</span>
-<pre>char *luaL_prepbuffsize (luaL_Buffer *B, size_t sz);</pre>
-<p>
-Returns an address to a space of size <code>sz</code>
-where you can copy a string to be added to buffer <code>B</code>
-(see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
-After copying the string into this space you must call
-<a href="#luaL_addsize"><code>luaL_addsize</code></a> with the size of the string to actually add
-it to the buffer.
-<hr><h3><a name="luaL_pushresult"><code>luaL_pushresult</code></a></h3><p>
-<span class="apii">[-?, +1, <em>e</em>]</span>
-<pre>void luaL_pushresult (luaL_Buffer *B);</pre>
-<p>
-Finishes the use of buffer <code>B</code> leaving the final string on
-the top of the stack.
-<hr><h3><a name="luaL_pushresultsize"><code>luaL_pushresultsize</code></a></h3><p>
-<span class="apii">[-?, +1, <em>e</em>]</span>
-<pre>void luaL_pushresultsize (luaL_Buffer *B, size_t sz);</pre>
-<p>
-Equivalent to the sequence <a href="#luaL_addsize"><code>luaL_addsize</code></a>, <a href="#luaL_pushresult"><code>luaL_pushresult</code></a>.
-<hr><h3><a name="luaL_ref"><code>luaL_ref</code></a></h3><p>
-<span class="apii">[-1, +0, <em>e</em>]</span>
-<pre>int luaL_ref (lua_State *L, int t);</pre>
-<p>
-Creates and returns a <em>reference</em>,
-in the table at index <code>t</code>,
-for the object at the top of the stack (and pops the object).
-<p>
-A reference is a unique integer key.
-As long as you do not manually add integer keys into table <code>t</code>,
-<a href="#luaL_ref"><code>luaL_ref</code></a> ensures the uniqueness of the key it returns.
-You can retrieve an object referred by reference <code>r</code>
-by calling <code>lua_rawgeti(L, t, r)</code>.
-Function <a href="#luaL_unref"><code>luaL_unref</code></a> frees a reference and its associated object.
-<p>
-If the object at the top of the stack is <b>nil</b>,
-<a href="#luaL_ref"><code>luaL_ref</code></a> returns the constant <a name="pdf-LUA_REFNIL"><code>LUA_REFNIL</code></a>.
-The constant <a name="pdf-LUA_NOREF"><code>LUA_NOREF</code></a> is guaranteed to be different
-from any reference returned by <a href="#luaL_ref"><code>luaL_ref</code></a>.
-<hr><h3><a name="luaL_Reg"><code>luaL_Reg</code></a></h3>
-<pre>typedef struct luaL_Reg {
-const char *name;
-lua_CFunction func;
-} luaL_Reg;</pre>
-<p>
-Type for arrays of functions to be registered by
-<a href="#luaL_setfuncs"><code>luaL_setfuncs</code></a>.
-<code>name</code> is the function name and <code>func</code> is a pointer to
-the function.
-Any array of <a href="#luaL_Reg"><code>luaL_Reg</code></a> must end with an sentinel entry
-in which both <code>name</code> and <code>func</code> are <code>NULL</code>.
-<hr><h3><a name="luaL_requiref"><code>luaL_requiref</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void luaL_requiref (lua_State *L, const char *modname,
-lua_CFunction openf, int glb);</pre>
-<p>
-Calls function <code>openf</code> with string <code>modname</code> as an argument
-and sets the call result in <code>package.loaded[modname]</code>,
-as if that function has been called through <a href="#pdf-require"><code>require</code></a>.
-<p>
-If <code>glb</code> is true,
-also stores the result into global <code>modname</code>.
-<p>
-Leaves a copy of that result on the stack.
-<hr><h3><a name="luaL_setfuncs"><code>luaL_setfuncs</code></a></h3><p>
-<span class="apii">[-nup, +0, <em>e</em>]</span>
-<pre>void luaL_setfuncs (lua_State *L, const luaL_Reg *l, int nup);</pre>
-<p>
-Registers all functions in the array <code>l</code>
-(see <a href="#luaL_Reg"><code>luaL_Reg</code></a>) into the table on the top of the stack
-(below optional upvalues, see next).
-<p>
-When <code>nup</code> is not zero,
-all functions are created sharing <code>nup</code> upvalues,
-which must be previously pushed on the stack
-on top of the library table.
-These values are popped from the stack after the registration.
-<hr><h3><a name="luaL_setmetatable"><code>luaL_setmetatable</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void luaL_setmetatable (lua_State *L, const char *tname);</pre>
-<p>
-Sets the metatable of the object at the top of the stack
-as the metatable associated with name <code>tname</code>
-in the registry (see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code></a>).
-<hr><h3><a name="luaL_testudata"><code>luaL_testudata</code></a></h3><p>
-<span class="apii">[-0, +0, <em>e</em>]</span>
-<pre>void *luaL_testudata (lua_State *L, int arg, const char *tname);</pre>
-<p>
-This function works like <a href="#luaL_checkudata"><code>luaL_checkudata</code></a>,
-except that, when the test fails,
-it returns <code>NULL</code> instead of throwing an error.
-<hr><h3><a name="luaL_tolstring"><code>luaL_tolstring</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>const char *luaL_tolstring (lua_State *L, int idx, size_t *len);</pre>
-<p>
-Converts any Lua value at the given index to a C&nbsp;string
-in a reasonable format.
-The resulting string is pushed onto the stack and also
-returned by the function.
-If <code>len</code> is not <code>NULL</code>,
-the function also sets <code>*len</code> with the string length.
-<p>
-If the value has a metatable with a <code>"__tostring"</code> field,
-then <code>luaL_tolstring</code> calls the corresponding metamethod
-with the value as argument,
-and uses the result of the call as its result.
-<hr><h3><a name="luaL_traceback"><code>luaL_traceback</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void luaL_traceback (lua_State *L, lua_State *L1, const char *msg,
-int level);</pre>
-<p>
-Creates and pushes a traceback of the stack <code>L1</code>.
-If <code>msg</code> is not <code>NULL</code> it is appended
-at the beginning of the traceback.
-The <code>level</code> parameter tells at which level
-to start the traceback.
-<hr><h3><a name="luaL_typename"><code>luaL_typename</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>const char *luaL_typename (lua_State *L, int index);</pre>
-<p>
-Returns the name of the type of the value at the given index.
-<hr><h3><a name="luaL_unref"><code>luaL_unref</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void luaL_unref (lua_State *L, int t, int ref);</pre>
-<p>
-Releases reference <code>ref</code> from the table at index <code>t</code>
-(see <a href="#luaL_ref"><code>luaL_ref</code></a>).
-The entry is removed from the table,
-so that the referred object can be collected.
-The reference <code>ref</code> is also freed to be used again.
-<p>
-If <code>ref</code> is <a href="#pdf-LUA_NOREF"><code>LUA_NOREF</code></a> or <a href="#pdf-LUA_REFNIL"><code>LUA_REFNIL</code></a>,
-<a href="#luaL_unref"><code>luaL_unref</code></a> does nothing.
-<hr><h3><a name="luaL_where"><code>luaL_where</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void luaL_where (lua_State *L, int lvl);</pre>
-<p>
-Pushes onto the stack a string identifying the current position
-of the control at level <code>lvl</code> in the call stack.
-Typically this string has the following format:
-<pre>
-<em>chunkname</em>:<em>currentline</em>:
-</pre><p>
-Level&nbsp;0 is the running function,
-level&nbsp;1 is the function that called the running function,
-etc.
-<p>
-This function is used to build a prefix for error messages.

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