Mercurial Hosting > luan
changeset 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 | 0a8e6fdb62f0 |
| files | docs/manual.html |
| diffstat | 1 files changed, 179 insertions(+), 5070 deletions(-) [+] |
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diff -r b5a926c481a5 -r c912f6de2053 docs/manual.html --- a/docs/manual.html Tue Oct 07 01:43:07 2014 +0000 +++ b/docs/manual.html Wed Oct 08 06:22:04 2014 +0000 @@ -66,6 +66,7 @@ <LI><A HREF="#3.3.5">3.3.5 – For Statement</A> <LI><A HREF="#3.3.6">3.3.6 – Function Calls as Statements</A> <LI><A HREF="#3.3.7">3.3.7 – Local Declarations</A> +<LI><A HREF="#3.3.8">3.3.8 – Or/And Statements</A> </UL> <LI><A HREF="#3.4">3.4 – Expressions</A> <UL> @@ -84,22 +85,8 @@ </UL> <P> <LI><A HREF="#4">4 – The Application Program Interface</A> -<UL> -<LI><A HREF="#4.1">4.1 – The Stack</A> -<LI><A HREF="#4.2">4.2 – Stack Size</A> -<LI><A HREF="#4.3">4.3 – Valid and Acceptable Indices</A> -<LI><A HREF="#4.4">4.4 – C Closures</A> -<LI><A HREF="#4.5">4.5 – Registry</A> -<LI><A HREF="#4.6">4.6 – Error Handling in C</A> -<LI><A HREF="#4.7">4.7 – Handling Yields in C</A> -<LI><A HREF="#4.8">4.8 – Functions and Types</A> -<LI><A HREF="#4.9">4.9 – The Debug Interface</A> -</UL> <P> <LI><A HREF="#5">5 – The Auxiliary Library</A> -<UL> -<LI><A HREF="#5.1">5.1 – Functions and Types</A> -</UL> <P> <LI><A HREF="#6">6 – Standard Libraries</A> <UL> @@ -133,48 +120,11 @@ <h1>1 – <a name="1">Introduction</a></h1> -<p> -Lua is an extension programming language designed to support -general procedural programming with data description -facilities. -It also offers good support for object-oriented programming, -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 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 functions to be called by Lua code. -Through the use of C 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>. +<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. + +<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. + +<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. <h1>2 – <a name="2">Basic Concepts</a></h1> @@ -186,7 +136,7 @@ <h2>2.1 – <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. @@ -194,7 +144,7 @@ <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. @@ -202,66 +152,42 @@ <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>thread</em>, and <em>table</em>. +<em>string</em>, <em>binary</em>, <em>function</em>, <em>userdata</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; -any other value makes it true. +<em>Boolean</em> is implemented as the Java class <em>Boolean</em>. <em>Number</em> represents real (double-precision floating-point) numbers. -Operations on numbers follow the same rules of -the underlying C implementation, -which, in turn, usually follows the IEEE 754 standard. -(It is easy to build Lua interpreters that use other -internal representations for numbers, -such as single-precision floats or long integers; -see file <code>luaconf.h</code>.) -<em>String</em> represents immutable sequences of bytes. - -Lua is 8-bit clean: -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 +<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 Java implementation. + +<em>String</em> is implemented as the Java class <em>String</em>. +<em>Binary</em> is implemented as the Java type <em>byte[]</em>. + + +<p> +Luan can call (and manipulate) functions written in Luan and +functions written in Java (see <a href="#3.4.9">§3.4.9</a>). <p> -The type <em>userdata</em> is provided to allow arbitrary C data to +The type <em>userdata</em> is provided to allow arbitrary Java objects to be stored in Lua variables. -A userdata value is a pointer to a block of raw memory. -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. -Userdata has no predefined operations in Lua, -except assignment and identity test. -By using <em>metatables</em>, -the programmer can define operations for full userdata values -(see <a href="#2.4">§2.4</a>). -Userdata values cannot be created or modified in Lua, -only through the C 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">§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. +A userdata value is a Java object that isn't of the standard Luan types. + + +<p> +Lua has a type <em>thread</em> that Luan lacks because Luan does not have the Lua concept of coroutines. <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 -(<em>Not a Number</em>, a special numeric value used to represent -undefined or unrepresentable results, such as <code>0/0</code>). +but with any Lua value except <b>nil</b>. 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. @@ -306,7 +232,7 @@ <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 @@ -350,30 +276,25 @@ <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">§4.5</a>). -In Lua, the variable <a href="#pdf-_G"><code>_G</code></a> is initialized with this same value. +This value is kept in the Luan state implemented in Java. +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 -with the global environment (see <a href="#pdf-load"><code>load</code></a>). -Therefore, by default, -global variables in Lua code refer to entries in the global environment. -Moreover, all standard libraries are loaded in the global environment -and several functions there operate on that environment. -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 -of its first upvalue.) - - -<p> -If you change the global environment in the registry -(through C code or the debug library), +it initializes the value of its <code>_ENV</code> to an empty table. +The values in the global environment become local variables of the chunk. +All standard libraries are loaded in the global environment +and so they become available as local variables. +You can use <a href="#pdf-load"><code>load</code></a> (or <a href="#pdf-loadfile"><code>load_file</code></a>) +to load a chunk with a specific environment instead of starting empty. + + +<p> +If you change the values in the global environment, 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. @@ -385,22 +306,13 @@ <h2>2.3 – <a name="2.3">Error Handling</a></h2> <p> -Because Lua is an embedded extension language, -all Lua actions start from C 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 -the compilation or execution of a Lua chunk, -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 +Luan error handling is quite different from Lua. + + +<p> +Luan 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, -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>. +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. <p> @@ -412,38 +324,24 @@ 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 – <a name="2.4">Metatables and Metamethods</a></h2> <p> -Every value in Lua can have a <em>metatable</em>. -This <em>metatable</em> is an ordinary Lua table -that defines the behavior of the original value +Every table in Luan can have a <em>metatable</em>. +This <em>metatable</em> is an ordinary Luan table +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. -For instance, when a non-numeric value is the operand of an addition, -Lua checks for a function in the field "<code>__add</code>" of the value's metatable. +of operations over a table by setting specific fields in its metatable. +For instance, when a table is the operand of an addition, +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; @@ -454,36 +352,27 @@ <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. -You cannot change the metatable of other types from Lua -(except by using the debug library); -you must use the C API for that. - - -<p> -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; -that is, there is one single metatable for all numbers, -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">§6.4</a>). - - -<p> -A metatable controls how an object behaves in arithmetic operations, +using the <a href="#pdf-setmetatable"><code>set_metatable</code></a> function. + + +<p> +Tables have individual metatables +(although multiple tables can share their metatables). +By default, a table has no metatable. + + +<p> +A metatable controls how a table behaves in arithmetic operations, order comparisons, concatenation, length operation, and indexing. -A metatable also can define a function to be called -when a userdata or a table is garbage collected. -When Lua performs one of these operations over a value, -it checks whether this value has a metatable with the corresponding event. +When Luan performs one of these operations over a table, +it checks whether this table 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> @@ -496,13 +385,13 @@ <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">§6.1</a>. In particular, to retrieve the metamethod of a given object, we use the expression @@ -513,21 +402,13 @@ 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> -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.) - +<p> <ul> @@ -538,14 +419,14 @@ <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> @@ -554,11 +435,11 @@ <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)) @@ -582,7 +463,7 @@ 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. @@ -610,7 +491,7 @@ <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. @@ -637,7 +518,7 @@ (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 @@ -674,7 +555,7 @@ <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 @@ -682,7 +563,7 @@ 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 @@ -700,9 +581,9 @@ 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 @@ -722,9 +603,9 @@ elseif type(op1) == "string" and type(op2) == "string" then return op1 < 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(···) end @@ -745,13 +626,13 @@ elseif type(op1) == "string" and type(op2) == "string" then return op1 <= 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(···) end @@ -760,7 +641,7 @@ end </pre><p> Note that, in the absence of a "le" metamethod, -Lua tries the "lt", assuming that <code>a <= b</code> is +Luan tries the "lt", assuming that <code>a <= b</code> is equivalent to <code>not (b < a)</code>. @@ -779,10 +660,10 @@ <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 @@ -808,14 +689,14 @@ <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 @@ -831,7 +712,7 @@ </li> <li><b>"call": </b> -called when Lua calls a value. +called when Luan calls a value. <pre> @@ -858,355 +739,17 @@ <h2>2.5 – <a name="2.5">Garbage Collection</a></h2> <p> -Lua performs automatic memory management. -This means that -you have to worry neither about allocating memory for new objects -nor about freeing it when the objects are no longer needed. -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 – <a name="2.5.1">Garbage-Collection Metamethods</a></h3> - -<p> -You can set garbage-collector metamethods for tables -and, using the C API, -for full userdata (see <a href="#2.4">§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 – <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 '<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. - - - - +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. + +<p> +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. <h2>2.6 – <a name="2.6">Coroutines</a></h2> <p> -Lua supports coroutines, -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>. +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. @@ -1215,7 +758,7 @@ <h1>3 – <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, @@ -1231,7 +774,7 @@ Non-terminals are shown like non-terminal, keywords are shown like <b>kword</b>, and other terminal symbols are shown like ‘<b>=</b>’. -The complete syntax of Lua can be found in <a href="#9">§9</a> +The complete syntax of Luan can be found in <a href="#9">§9</a> at the end of this manual. @@ -1239,11 +782,15 @@ <h2>3.1 – <a name="3.1">Lexical Conventions</a></h2> <p> -Lua is a free-form language. -It ignores spaces (including new lines) and comments +Luan ignores spaces 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> @@ -1266,6 +813,14 @@ 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> @@ -1281,7 +836,7 @@ <pre> + - * / % ^ # == ~= <= >= < > = - ( ) { } [ ] :: + ( ) { } [ ] ; : , . .. ... </pre> @@ -1344,16 +899,6 @@ 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, @@ -1444,9 +989,9 @@ </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">§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.) @@ -1498,34 +1043,6 @@ stat ::= ‘<b>;</b>’ </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: @@ -1535,9 +1052,6 @@ </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">§3.3.4</a>). @@ -1574,13 +1088,6 @@ 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. - - @@ -1675,15 +1182,13 @@ 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">§3.3.5</a>). +Lua also has a <b>for</b> statement (see <a href="#3.3.5">§3.3.5</a>). <p> The condition expression of a -control structure can return any value. -Both <b>false</b> and <b>nil</b> are considered false. -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). +control structure must return a boolean. +This is unlike Lua and is intended to catch programming errors more quickly. <p> @@ -1694,31 +1199,6 @@ 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 ::= ‘<b>::</b>’ Name ‘<b>::</b>’ -</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> @@ -1744,94 +1224,19 @@ stat ::= <b>return</b> [explist] [‘<b>;</b>’] </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 – <a name="3.3.5">For Statement</a></h3> -<p> - -The <b>for</b> statement has two forms: -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 ‘<b>=</b>’ exp ‘<b>,</b>’ exp [‘<b>,</b>’ 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> > 0 and <em>var</em> <= <em>limit</em>) or (<em>step</em> <= 0 and <em>var</em> >= <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 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, + +<p> +The <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> @@ -1840,17 +1245,16 @@ A <b>for</b> statement like <pre> - for <em>var_1</em>, ···, <em>var_n</em> in <em>explist</em> do <em>block</em> end + for <em>var_1</em>, ···, <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>, ···, <em>var_n</em> = <em>f</em>(<em>s</em>, <em>var</em>) + local <em>var_1</em>, ···, <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 @@ -1860,15 +1264,13 @@ <ul> <li> -<code><em>explist</em></code> is evaluated only once. -Its results are an <em>iterator</em> function, -a <em>state</em>, -and an initial value for the first <em>iterator variable</em>. +<code><em>expression</em></code> is evaluated only once. +Its result is an <em>iterator</em> function. </li> <li> -<code><em>f</em></code>, <code><em>s</em></code>, and <code><em>var</em></code> are invisible variables. -The names are here for explanatory purposes only. +<code><em>f</em></code> is an invisible variable. +The name is here for explanatory purposes only. </li> <li> @@ -1884,7 +1286,8 @@ </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 – <a name="3.3.6">Function Calls as Statements</a></h3><p> @@ -1912,7 +1315,6 @@ of a multiple assignment (see <a href="#3.3.3">§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">§3.3.2</a>), and so local variables can be declared in a chunk outside any explicit block. @@ -1923,6 +1325,18 @@ +<h3>3.3.8 – <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> + + @@ -1930,7 +1344,7 @@ <h2>3.4 – <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 @@ -2014,7 +1428,7 @@ <h3>3.4.1 – <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); @@ -2027,7 +1441,7 @@ 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. @@ -2039,7 +1453,7 @@ <h3>3.4.2 – <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. @@ -2055,7 +1469,7 @@ <h3>3.4.3 – <a name="3.4.3">Relational Operators</a></h3><p> -The relational operators in Lua are +The relational operators in Luan are <pre> == ~= < > <= >= @@ -2080,7 +1494,7 @@ <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">§2.4</a>). @@ -2149,7 +1563,7 @@ <h3>3.4.5 – <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">§3.4.2</a>. @@ -2198,7 +1612,7 @@ <h3>3.4.7 – <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> @@ -2281,7 +1695,7 @@ <h3>3.4.9 – <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 @@ -2298,16 +1712,7 @@ <p> -The form - -<pre> - functioncall ::= prefixexp ‘<b>:</b>’ 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. - +Lua supports a special function call for "methods" like <em>obj:fn(args)</em> . Luan does not support this. <p> Arguments have the following syntax: @@ -2330,7 +1735,7 @@ <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. @@ -2371,7 +1776,7 @@ <pre> stat ::= <b>function</b> funcname funcbody stat ::= <b>local</b> <b>function</b> Name funcbody - funcname ::= Name {‘<b>.</b>’ Name} [‘<b>:</b>’ Name] + funcname ::= Name {‘<b>.</b>’ Name} </pre><p> The statement @@ -2415,9 +1820,9 @@ <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. @@ -2483,38 +1888,13 @@ 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 – <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. @@ -2575,3083 +1955,11 @@ <h1>4 – <a name="4">The Application Program Interface</a></h1> <p> - -This section describes the C API for Lua, that is, -the set of C functions available to the host program to communicate -with Lua. -All API functions and related types and constants -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 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 – <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 functions that are still active. -This stack initially contains any arguments to the C function -and it is where the C 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 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 1 represents the first element -(that is, the element that was pushed onto the stack first) -and -index <em>n</em> represents the last element; -index -1 also represents the last element -(that is, the element at the top) -and index <em>-n</em> represents the first element. - - - - - -<h2>4.2 – <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 – <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 1 and the stack top -(<code>1 ≤ abs(index) ≤ 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 code -but which are not in the stack. -Pseudo-indices are used to access the registry -and the upvalues of a C function (see <a href="#4.4">§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 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 – <a name="4.4">C Closures</a></h2> - -<p> -When a C function is created, -it is possible to associate some values with it, -thus creating a <em>C 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 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 – <a name="4.5">Registry</a></h2> - -<p> -Lua provides a <em>registry</em>, -a predefined table that can be used by any C 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 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 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 – <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">§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">§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 function you can throw an error by calling <a href="#lua_error"><code>lua_error</code></a>. - - - - - -<h2>4.7 – <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 – <a name="4.8">Functions and Types</a></h2> - -<p> -Here we list all functions and types from the C 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, –]</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 >= 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 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 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, –]</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">§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 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">§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 functions. - - -<p> -In order to communicate properly with Lua, -a C function must use the following protocol, -which defines the way parameters and results are passed: -a C 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 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 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 <= 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, –]</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, –]</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 0. -Also returns 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><</code>)</li> -<li><b><a name="pdf-LUA_OPLE"><code>LUA_OPLE</code></a>: </b> compares for less or equal (<code><=</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> is 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">§3.4.5</a>). - - - - - -<hr><h3><a name="lua_copy"><code>lua_copy</code></a></h3><p> -<span class="apii">[-0, +0, –]</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 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">§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">§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">§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, –]</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, –]</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">§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">§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), –]</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 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">§2.4</a>). - - - - - -<hr><h3><a name="lua_gettop"><code>lua_gettop</code></a></h3><p> -<span class="apii">[-0, +0, –]</span> -<pre>int lua_gettop (lua_State *L);</pre> - -<p> -Returns the index of the top element in the stack. -Because indices start at 1, -this result is equal to the number of elements in the stack -(and so 0 means an empty stack). - - - - - -<hr><h3><a name="lua_getuservalue"><code>lua_getuservalue</code></a></h3><p> -<span class="apii">[-0, +1, –]</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, –]</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, –]</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 otherwise. - - - - - -<hr><h3><a name="lua_iscfunction"><code>lua_iscfunction</code></a></h3><p> -<span class="apii">[-0, +0, –]</span> -<pre>int lua_iscfunction (lua_State *L, int index);</pre> - -<p> -Returns 1 if the value at the given index is a C function, -and 0 otherwise. - - - - - -<hr><h3><a name="lua_isfunction"><code>lua_isfunction</code></a></h3><p> -<span class="apii">[-0, +0, –]</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 otherwise. - - - - - -<hr><h3><a name="lua_islightuserdata"><code>lua_islightuserdata</code></a></h3><p> -<span class="apii">[-0, +0, –]</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 otherwise. - - - - - -<hr><h3><a name="lua_isnil"><code>lua_isnil</code></a></h3><p> -<span class="apii">[-0, +0, –]</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 otherwise. - - - - - -<hr><h3><a name="lua_isnone"><code>lua_isnone</code></a></h3><p> -<span class="apii">[-0, +0, –]</span> -<pre>int lua_isnone (lua_State *L, int index);</pre> - -<p> -Returns 1 if the given index is not valid, -and 0 otherwise. - - - - - -<hr><h3><a name="lua_isnoneornil"><code>lua_isnoneornil</code></a></h3><p> -<span class="apii">[-0, +0, –]</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 otherwise. - - - - - -<hr><h3><a name="lua_isnumber"><code>lua_isnumber</code></a></h3><p> -<span class="apii">[-0, +0, –]</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 otherwise. - - - - - -<hr><h3><a name="lua_isstring"><code>lua_isstring</code></a></h3><p> -<span class="apii">[-0, +0, –]</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 otherwise. - - - - - -<hr><h3><a name="lua_istable"><code>lua_istable</code></a></h3><p> -<span class="apii">[-0, +0, –]</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 otherwise. - - - - - -<hr><h3><a name="lua_isthread"><code>lua_isthread</code></a></h3><p> -<span class="apii">[-0, +0, –]</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 otherwise. - - - - - -<hr><h3><a name="lua_isuserdata"><code>lua_isuserdata</code></a></h3><p> -<span class="apii">[-0, +0, –]</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 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">§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, –]</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">§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">§4.5</a>). -When loading main chunks, -this upvalue will be the <code>_ENV</code> variable (see <a href="#2.2">§2.2</a>). - - - - - -<hr><h3><a name="lua_newstate"><code>lua_newstate</code></a></h3><p> -<span class="apii">[-0, +0, –]</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–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), –]</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), –]</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">§4.7</a>). - - - - - -<hr><h3><a name="lua_pop"><code>lua_pop</code></a></h3><p> -<span class="apii">[-n, +0, –]</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, –]</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 closure onto the stack. - - -<p> -When a C function is created, -it is possible to associate some values with it, -thus creating a C closure (see <a href="#4.4">§4.4</a>); -these values are then accessible to the function whenever it is called. -To associate values with a C 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 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 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, –]</span> -<pre>void lua_pushcfunction (lua_State *L, lua_CFunction f);</pre> - -<p> -Pushes a C 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 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 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, –]</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, –]</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, –]</span> -<pre>void lua_pushlightuserdata (lua_State *L, void *p);</pre> - -<p> -Pushes a light userdata onto the stack. - - -<p> -Userdata represent C 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 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, –]</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, –]</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, –]</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, –]</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, –]</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, –]</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 0. -Also returns 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, –]</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, –]</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, –]</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, –]</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 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, –]</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, –]</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">[-?, +?, –]</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, –]</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">§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, –]</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">§2.4</a>). - - - - - -<hr><h3><a name="lua_settop"><code>lua_settop</code></a></h3><p> -<span class="apii">[-?, +?, –]</span> -<pre>void lua_settop (lua_State *L, int index);</pre> - -<p> -Accepts any index, or 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 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, –]</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, –]</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, –]</span> -<pre>int lua_toboolean (lua_State *L, int index);</pre> - -<p> -Converts the Lua value at the given index to a C boolean -value (0 or 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, –]</span> -<pre>lua_CFunction lua_tocfunction (lua_State *L, int index);</pre> - -<p> -Converts a value at the given index to a C function. -That value must be a C function; -otherwise, returns <code>NULL</code>. - - - - - -<hr><h3><a name="lua_tointeger"><code>lua_tointeger</code></a></h3><p> -<span class="apii">[-0, +0, –]</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, –]</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">§3.4.2</a>); -otherwise, <code>lua_tointegerx</code> returns 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 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 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, –]</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, –]</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 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">§3.4.2</a>); -otherwise, <a href="#lua_tonumberx"><code>lua_tonumberx</code></a> returns 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, –]</span> -<pre>const void *lua_topointer (lua_State *L, int index);</pre> - -<p> -Converts the value at the given index to a generic -C 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, –]</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, –]</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, –]</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">§3.4.2</a>); -otherwise, <code>lua_tounsignedx</code> returns 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, –]</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, –]</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, –]</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, –]</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">§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 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">[-?, +?, –]</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">[-?, +?, –]</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">§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">[-?, +?, –]</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 function, as follows: - -<pre> - return lua_yieldk (L, n, i, k); -</pre><p> -When a C 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">§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 – <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 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 for C functions). -</li> - -<li><b><code>isvararg</code>: </b> -true if the function is a vararg function -(always true for C functions). -</li> - -</ul> - - - - -<hr><h3><a name="lua_gethook"><code>lua_gethook</code></a></h3><p> -<span class="apii">[-0, +0, –]</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, –]</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, –]</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>></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, ">S", &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), –]</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, –]</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 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), –]</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 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, –]</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, –]</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, –]</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, –]</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, –]</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>. - - - +In the Lua documentation, +this section described the C API for Lua. +Obviously this is not relevant for Luan. +The implementation of Luan is radically different from Lua and will be documented eventually in Javadoc. +So this section is just a placeholder so that Luan documentation can match Lua's documentation. @@ -5659,1207 +1967,8 @@ <h1>5 – <a name="5">The Auxiliary Library</a></h1> <p> - -The <em>auxiliary library</em> provides several convenient functions -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 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 – <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 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 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, &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(&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, &b, sz)</code>.</li> - -<li>Then copy the string into that space.</li> - -<li> -Finish by calling <code>luaL_pushresultsize(&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, –]</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 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, –]</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, +?, –]</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 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, –]</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">§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, –]</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, –]</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, –]</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, –]</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 C <code>realloc</code> function -and then sets a panic function (see <a href="#4.6">§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, –]</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 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, –]</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, –]</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 0 is the running function, -level 1 is the function that called the running function, -etc. - - -<p> -This function is used to build a prefix for error messages. - - +Like the previous section, this section is specific to Lua and is not relevant to Luan. +So this section is just a placeholder.