repo/luan: website/src/manual.html.luan comparison

comparison website/src/manual.html.luan @ 418:455784e2227d

remove C documentation from manual

author	Franklin Schmidt <fschmidt@gmail.com>
date	Thu, 30 Apr 2015 21:52:20 -0600
parents	a40e99cf0b0b
children	df95199ca4c0

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 <p>
 The loop creates ten closures
 (that is, ten instances of the anonymous function).
 Each of these closures uses a different <tt>y</tt> variable,
 while all of them share the same <tt>x</tt>.
-<h1>4 &ndash; <a name="4">The Application Program Interface</a></h1>
-<p>
-This section describes the C&nbsp;API for Lua, that is,
-the set of C&nbsp;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&nbsp;libraries,
-the Lua API functions do not check their arguments for validity or consistency.
-However, you can change this behavior by compiling Lua
-with the macro <a name="pdf-LUA_USE_APICHECK"><code>LUA_USE_APICHECK</code></a> defined.
-<h2>4.1 &ndash; <a name="4.1">The Stack</a></h2>
-<p>
-Lua uses a <em>virtual stack</em> to pass values to and from C.
-Each element in this stack represents a Lua value
-(<b>nil</b>, number, string, etc.).
-<p>
-Whenever Lua calls C, the called function gets a new stack,
-which is independent of previous stacks and of stacks of
-C&nbsp;functions that are still active.
-This stack initially contains any arguments to the C&nbsp;function
-and it is where the C&nbsp;function pushes its results
-to be returned to the caller (see <a href="#lua_CFunction"><code>lua_CFunction</code></a>).
-<p>
-For convenience,
-most query operations in the API do not follow a strict stack discipline.
-Instead, they can refer to any element in the stack
-by using an <em>index</em>:
-A positive index represents an absolute stack position
-(starting at&nbsp;1);
-a negative index represents an offset relative to the top of the stack.
-More specifically, if the stack has <em>n</em> elements,
-then index&nbsp;1 represents the first element
-(that is, the element that was pushed onto the stack first)
-and
-index&nbsp;<em>n</em> represents the last element;
-index&nbsp;-1 also represents the last element
-(that is, the element at the&nbsp;top)
-and index <em>-n</em> represents the first element.
-<h2>4.2 &ndash; <a name="4.2">Stack Size</a></h2>
-<p>
-When you interact with the Lua API,
-you are responsible for ensuring consistency.
-In particular,
-<em>you are responsible for controlling stack overflow</em>.
-You can use the function <a href="#lua_checkstack"><code>lua_checkstack</code></a>
-to ensure that the stack has enough space for pushing new elements.
-<p>
-Whenever Lua calls C,
-it ensures that the stack has space for
-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 space for all results,
-but it does not ensure any extra space.
-So, before pushing anything in the stack after such a call
-you should use <a href="#lua_checkstack"><code>lua_checkstack</code></a>.
-<h2>4.3 &ndash; <a name="4.3">Valid and Acceptable Indices</a></h2>
-<p>
-Any function in the API that receives stack indices
-works only with <em>valid indices</em> or <em>acceptable indices</em>.
-<p>
-A <em>valid index</em> is an index that refers to a
-real position within the stack, that is,
-its position lies between&nbsp;1 and the stack top
-(<code>1 &le; abs(index) &le; top</code>).
-Usually, functions that can modify the value at an index
-require valid indices.
-<p>
-Unless otherwise noted,
-any function that accepts valid indices also accepts <em>pseudo-indices</em>,
-which represent some Lua values that are accessible to C&nbsp;code
-but which are not in the stack.
-Pseudo-indices are used to access the registry
-and the upvalues of a C&nbsp;function (see <a href="#4.4">&sect;4.4</a>).
-<p>
-Functions that do not need a specific stack position,
-but only a value in the stack (e.g., query functions),
-can be called with acceptable indices.
-An <em>acceptable index</em> can be any valid index,
-including the pseudo-indices,
-but it also can be any positive index after the stack top
-within the space allocated for the stack,
-that is, indices up to the stack size.
-(Note that 0 is never an acceptable index.)
-Except when noted otherwise,
-functions in the API work with acceptable indices.
-<p>
-Acceptable indices serve to avoid extra tests
-against the stack top when querying the stack.
-For instance, a C&nbsp;function can query its third argument
-without the need to first check whether there is a third argument,
-that is, without the need to check whether 3 is a valid index.
-<p>
-For functions that can be called with acceptable indices,
-any non-valid index is treated as if it
-contains a value of a virtual type <a name="pdf-LUA_TNONE"><code>LUA_TNONE</code></a>,
-which behaves like a nil value.
-<h2>4.4 &ndash; <a name="4.4">C Closures</a></h2>
-<p>
-When a C&nbsp;function is created,
-it is possible to associate some values with it,
-thus creating a <em>C&nbsp;closure</em>
-(see <a href="#lua_pushcclosure"><code>lua_pushcclosure</code></a>);
-these values are called <em>upvalues</em> and are
-accessible to the function whenever it is called.
-<p>
-Whenever a C&nbsp;function is called,
-its upvalues are located at specific pseudo-indices.
-These pseudo-indices are produced by the macro
-<a href="#lua_upvalueindex"><code>lua_upvalueindex</code></a>.
-The first value associated with a function is at position
-<code>lua_upvalueindex(1)</code>, and so on.
-Any access to <code>lua_upvalueindex(<em>n</em>)</code>,
-where <em>n</em> is greater than the number of upvalues of the
-current function (but not greater than 256),
-produces an acceptable but invalid index.
-<h2>4.5 &ndash; <a name="4.5">Registry</a></h2>
-<p>
-Lua provides a <em>registry</em>,
-a predefined table that can be used by any C&nbsp;code to
-store whatever Lua values it needs to store.
-The registry table is always located at pseudo-index
-<a name="pdf-LUA_REGISTRYINDEX"><code>LUA_REGISTRYINDEX</code></a>,
-which is a valid index.
-Any C&nbsp;library can store data into this table,
-but it must take care to choose keys
-that are different from those used
-by other libraries, to avoid collisions.
-Typically, you should use as key a string containing your library name,
-or a light userdata with the address of a C&nbsp;object in your code,
-or any Lua object created by your code.
-As with variable 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 (see <a href="#luaL_ref"><code>luaL_ref</code></a>)
-and by some predefined values.
-Therefore, integer keys must not be used for other purposes.
-<p>
-When you create a new Lua state,
-its registry comes with some predefined values.
-These predefined values are indexed with integer keys
-defined as constants in <code>lua.h</code>.
-The following constants are defined:
-<ul>
-<li><b><a name="pdf-LUA_RIDX_MAINTHREAD"><code>LUA_RIDX_MAINTHREAD</code></a>: </b> At this index the registry has
-the main thread of the state.
-(The main thread is the one created together with the state.)
-</li>
-<li><b><a name="pdf-LUA_RIDX_GLOBALS"><code>LUA_RIDX_GLOBALS</code></a>: </b> At this index the registry has
-the global environment.
-</li>
-</ul>
-<h2>4.6 &ndash; <a name="4.6">Error Handling in C</a></h2>
-<p>
-Internally, Lua uses the C <code>longjmp</code> facility to handle errors.
-(Lua will use exceptions if you compile it as C++;
-search for <code>LUAI_THROW</code> in the source code for details.)
-When Lua faces any error
-(such as a memory allocation error, type errors, syntax errors,
-and runtime errors)
-it <em>raises</em> an error;
-that is, it does a long jump.
-A <em>protected environment</em> uses <code>setjmp</code>
-to set a recovery point;
-any error jumps to the most recent active recovery point.
-<p>
-If an error happens outside any protected environment,
-Lua calls a <em>panic function</em> (see <a href="#lua_atpanic"><code>lua_atpanic</code></a>)
-and then calls <code>abort</code>,
-thus exiting the host application.
-Your panic function can avoid this exit by
-never returning
-(e.g., doing a long jump to your own recovery point outside Lua).
-<p>
-The panic function runs as if it were a message handler (see <a href="#2.3">&sect;2.3</a>);
-in particular, the error message is at the top of the stack.
-However, there is no guarantee about stack space.
-To push anything on the stack,
-the panic function must first check the available space (see <a href="#4.2">&sect;4.2</a>).
-<p>
-Most functions in the API can raise an error,
-for instance due to a memory allocation error.
-The documentation for each function indicates whether
-it can raise errors.
-<p>
-Inside a C&nbsp;function you can raise an error by calling <a href="#lua_error"><code>lua_error</code></a>.
-<h2>4.7 &ndash; <a name="4.7">Handling Yields in C</a></h2>
-<p>
-Internally, Lua uses the C <code>longjmp</code> facility to yield a coroutine.
-Therefore, if a C 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 named <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>
-As an illustration, consider the following function:
-<pre>
-int original_function (lua_State *L) {
-...     /* code 1 */
-status = lua_pcall(L, n, m, h);  /* calls Lua */
-...     /* code 2 */
-}
-</pre><p>
-Now we want to allow
-the Lua code being run by <a href="#lua_pcall"><code>lua_pcall</code></a> to yield.
-First, we can rewrite our function like here:
-<pre>
-int k (lua_State *L, int status, lua_KContext ctx) {
-...  /* code 2 */
-}
-int original_function (lua_State *L) {
-...     /* code 1 */
-return k(L, lua_pcall(L, n, m, h), ctx);
-}
-</pre><p>
-In the above code,
-the new function <code>k</code> is a
-<em>continuation function</em> (with type <a href="#lua_KFunction"><code>lua_KFunction</code></a>),
-which should do all the work that the original function
-was doing after calling <a href="#lua_pcall"><code>lua_pcall</code></a>.
-Now, we must inform Lua that it must call <code>k</code> if the Lua code
-being executed by <a href="#lua_pcall"><code>lua_pcall</code></a> gets interrupted in some way
-(errors or yielding),
-so we rewrite the code as here,
-replacing <a href="#lua_pcall"><code>lua_pcall</code></a> by <a href="#lua_pcallk"><code>lua_pcallk</code></a>:
-<pre>
-int original_function (lua_State *L) {
-...     /* code 1 */
-return k(L, lua_pcallk(L, n, m, h, ctx2, k), ctx1);
-}
-</pre><p>
-Note the external, explicit call to the continuation:
-Lua will call the continuation only if needed, that is,
-in case of errors or resuming after a yield.
-If the called function returns normally without ever yielding,
-<a href="#lua_pcallk"><code>lua_pcallk</code></a> (and <a href="#lua_callk"><code>lua_callk</code></a>) will also return normally.
-(Of course, instead of calling the continuation in that case,
-you can do the equivalent work directly inside the original function.)
-<p>
-Besides the Lua state,
-the continuation function has two other parameters:
-the final status of the call plus the context value (<code>ctx</code>) that
-was passed originally to <a href="#lua_pcallk"><code>lua_pcallk</code></a>.
-(Lua does not use this context value;
-it only passes this value from the original function to the
-continuation function.)
-For <a href="#lua_pcallk"><code>lua_pcallk</code></a>,
-the status is the same value that would be returned by <a href="#lua_pcallk"><code>lua_pcallk</code></a>,
-except that it is <a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a> when being executed after a yield
-(instead of <a href="#pdf-LUA_OK"><code>LUA_OK</code></a>).
-For <a href="#lua_yieldk"><code>lua_yieldk</code></a> and <a href="#lua_callk"><code>lua_callk</code></a>,
-the status is always <a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a> when Lua calls the continuation.
-(For these two functions,
-Lua will not call the continuation in case of errors,
-because they do not handle errors.)
-Similarly, when using <a href="#lua_callk"><code>lua_callk</code></a>,
-you should call the continuation function
-with <a href="#pdf-LUA_OK"><code>LUA_OK</code></a> as the status.
-(For <a href="#lua_yieldk"><code>lua_yieldk</code></a>, there is not much point in calling
-directly the continuation function,
-because <a href="#lua_yieldk"><code>lua_yieldk</code></a> usually does not return.)
-<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.
-<h2>4.8 &ndash; <a name="4.8">Functions and Types</a></h2>
-<p>
-Here we list all functions and types from the C&nbsp;API in
-alphabetical order.
-Each function has an indicator like this:
-<span class="apii">[-o, +p, <em>x</em>]</span>
-<p>
-The first field, <code>o</code>,
-is how many elements the function pops from the stack.
-The second field, <code>p</code>,
-is how many elements the function pushes onto the stack.
-(Any function always pushes its results after popping its arguments.)
-A field in the form <code>x|y</code> means the function can push (or pop)
-<code>x</code> or <code>y</code> elements,
-depending on the situation;
-an interrogation mark '<code>?</code>' means that
-we cannot know how many elements the function pops/pushes
-by looking only at its arguments
-(e.g., they may depend on what is on the stack).
-The third field, <code>x</code>,
-tells whether the function may raise errors:
-'<code>-</code>' means the function never raises any error;
-'<code>e</code>' means the function may raise errors;
-'<code>v</code>' means the function may raise an error on purpose.
-<hr><h3><a name="lua_absindex"><code>lua_absindex</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_absindex (lua_State *L, int idx);</pre>
-<p>
-Converts the acceptable index <code>idx</code> into an absolute index
-(that is, one that does not depend on the stack top).
-<hr><h3><a name="lua_Alloc"><code>lua_Alloc</code></a></h3>
-<pre>typedef void * (*lua_Alloc) (void *ud,
-void *ptr,
-size_t osize,
-size_t nsize);</pre>
-<p>
-The type of the memory-allocation function used by Lua states.
-The allocator function must provide a
-functionality similar to <code>realloc</code>,
-but not exactly the same.
-Its arguments are
-<code>ud</code>, an opaque pointer passed to <a href="#lua_newstate"><code>lua_newstate</code></a>;
-<code>ptr</code>, a pointer to the block being allocated/reallocated/freed;
-<code>osize</code>, the original size of the block or some code about what
-is being allocated;
-and <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 must behave like <code>free</code>
-and return <code>NULL</code>.
-<p>
-When <code>nsize</code> is not zero,
-the allocator must behave like <code>realloc</code>.
-The allocator returns <code>NULL</code>
-if and only if it cannot fulfill the request.
-Lua assumes that the allocator never fails when
-<code>osize &gt;= nsize</code>.
-<p>
-Here is a simple implementation for the allocator function.
-It is used in the auxiliary library by <a href="#luaL_newstate"><code>luaL_newstate</code></a>.
-<pre>
-static void *l_alloc (void *ud, void *ptr, size_t osize,
-size_t nsize) {
-(void)ud;  (void)osize;  /* not used */
-if (nsize == 0) {
-free(ptr);
-return NULL;
-}
-else
-return realloc(ptr, nsize);
-}
-</pre><p>
-Note that Standard&nbsp;C ensures
-that <code>free(NULL)</code> has no effect and that
-<code>realloc(NULL,size)</code> is equivalent to <code>malloc(size)</code>.
-This code assumes that <code>realloc</code> does not fail when shrinking a block.
-(Although Standard&nbsp;C does not ensure this behavior,
-it seems to be a safe assumption.)
-<hr><h3><a name="lua_arith"><code>lua_arith</code></a></h3><p>
-<span class="apii">[-(2|1), +1, <em>e</em>]</span>
-<pre>void lua_arith (lua_State *L, int op);</pre>
-<p>
-Performs an arithmetic or bitwise operation over the two values
-(or one, in the case of negations)
-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 float division (<code>/</code>)</li>
-<li><b><a name="pdf-LUA_OPIDIV"><code>LUA_OPIDIV</code></a>: </b> performs floor 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>
-<li><b><a name="pdf-LUA_OPBNOT"><code>LUA_OPBNOT</code></a>: </b> performs bitwise negation (<code>~</code>)</li>
-<li><b><a name="pdf-LUA_OPBAND"><code>LUA_OPBAND</code></a>: </b> performs bitwise and (<code>&amp;</code>)</li>
-<li><b><a name="pdf-LUA_OPBOR"><code>LUA_OPBOR</code></a>: </b> performs bitwise or (<code>|</code>)</li>
-<li><b><a name="pdf-LUA_OPBXOR"><code>LUA_OPBXOR</code></a>: </b> performs bitwise exclusive or (<code>~</code>)</li>
-<li><b><a name="pdf-LUA_OPSHL"><code>LUA_OPSHL</code></a>: </b> performs left shift (<code>&lt;&lt;</code>)</li>
-<li><b><a name="pdf-LUA_OPSHR"><code>LUA_OPSHR</code></a>: </b> performs right shift (<code>&gt;&gt;</code>)</li>
-</ul>
-<hr><h3><a name="lua_atpanic"><code>lua_atpanic</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_CFunction lua_atpanic (lua_State *L, lua_CFunction panicf);</pre>
-<p>
-Sets a new panic function and returns the old one (see <a href="#4.6">&sect;4.6</a>).
-<hr><h3><a name="lua_call"><code>lua_call</code></a></h3><p>
-<span class="apii">[-(nargs+1), +nresults, <em>e</em>]</span>
-<pre>void lua_call (lua_State *L, int nargs, int nresults);</pre>
-<p>
-Calls a function.
-<p>
-To call a function you must use the following protocol:
-first, the function to be called is pushed onto the stack;
-then, the arguments to the function are pushed
-in direct order;
-that is, the first argument is pushed first.
-Finally you call <a href="#lua_call"><code>lua_call</code></a>;
-<code>nargs</code> is the number of arguments that you pushed onto the stack.
-All arguments and the function value are popped from the stack
-when the function is called.
-The function results are pushed onto the stack when the function returns.
-The number of results is adjusted to <code>nresults</code>,
-unless <code>nresults</code> is <a name="pdf-LUA_MULTRET"><code>LUA_MULTRET</code></a>.
-In this case, all results from the function are pushed.
-Lua takes care that the returned values fit into the stack space.
-The function results are pushed onto the stack in direct order
-(the first result is pushed first),
-so that after the call the last result is on the top of the stack.
-<p>
-Any error inside the called function is propagated upwards
-(with a <code>longjmp</code>).
-<p>
-The following example shows how the host program can do the
-equivalent to this Lua code:
-<pre>
-a = f("how", t.x, 14)
-</pre><p>
-Here it is in&nbsp;C:
-<pre>
-lua_getglobal(L, "f");                  /* function to be called */
-lua_pushliteral(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 <em>balanced</em>:
-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,
-lua_KContext ctx,
-lua_KFunction k);</pre>
-<p>
-This function behaves exactly like <a href="#lua_call"><code>lua_call</code></a>,
-but allows the called function to yield (see <a href="#4.7">&sect;4.7</a>).
-<hr><h3><a name="lua_CFunction"><code>lua_CFunction</code></a></h3>
-<pre>typedef int (*lua_CFunction) (lua_State *L);</pre>
-<p>
-Type for C&nbsp;functions.
-<p>
-In order to communicate properly with Lua,
-a C&nbsp;function must use the following protocol,
-which defines the way parameters and results are passed:
-a C&nbsp;function receives its arguments from Lua in its stack
-in direct order (the first argument is pushed first).
-So, when the function starts,
-<code>lua_gettop(L)</code> returns the number of arguments received by the function.
-The first argument (if any) is at index 1
-and its last argument is at index <code>lua_gettop(L)</code>.
-To return values to Lua, a C&nbsp;function just pushes them onto the stack,
-in direct order (the first result is pushed first),
-and returns the number of results.
-Any other value in the stack below the results will be properly
-discarded by Lua.
-Like a Lua function, a C&nbsp;function called by Lua can also return
-many results.
-<p>
-As an example, the following function receives a variable number
-of numerical arguments and returns their average and their sum:
-<pre>
-static int foo (lua_State *L) {
-int n = lua_gettop(L);    /* number of arguments */
-lua_Number sum = 0.0;
-int i;
-for (i = 1; i &lt;= n; i++) {
-if (!lua_isnumber(L, i)) {
-lua_pushliteral(L, "incorrect argument");
-lua_error(L);
-}
-sum += lua_tonumber(L, i);
-}
-lua_pushnumber(L, sum/n);        /* first result */
-lua_pushnumber(L, sum);         /* second result */
-return 2;                   /* number of results */
-}
-</pre>
-<hr><h3><a name="lua_checkstack"><code>lua_checkstack</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_checkstack (lua_State *L, int n);</pre>
-<p>
-Ensures that the stack has space for at least <code>n</code> extra slots.
-It returns false if it cannot fulfill the request,
-either because it would cause the stack
-to be larger than a fixed maximum size
-(typically at least several thousand elements) or
-because it cannot allocate memory for the extra space.
-This function never shrinks the stack;
-if the stack is already larger than the new size,
-it is left unchanged.
-<hr><h3><a name="lua_close"><code>lua_close</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void lua_close (lua_State *L);</pre>
-<p>
-Destroys all objects in the given Lua state
-(calling the corresponding garbage-collection metamethods, if any)
-and frees all dynamic memory used by this state.
-On several platforms, you may not need to call this function,
-because all resources are naturally released when the host program ends.
-On the other hand, long-running programs that create multiple states,
-such as daemons or web servers,
-will probably need to close states as soon as they are not needed.
-<hr><h3><a name="lua_compare"><code>lua_compare</code></a></h3><p>
-<span class="apii">[-0, +0, <em>e</em>]</span>
-<pre>int lua_compare (lua_State *L, int index1, int index2, int op);</pre>
-<p>
-Compares two Lua values.
-Returns 1 if the value at index <code>index1</code> satisfies <code>op</code>
-when compared with the value at index <code>index2</code>,
-following the semantics of the corresponding Lua operator
-(that is, it may call metamethods).
-Otherwise returns&nbsp;0.
-Also returns&nbsp;0 if any of the indices is not valid.
-<p>
-The value of <code>op</code> must be one of the following constants:
-<ul>
-<li><b><a name="pdf-LUA_OPEQ"><code>LUA_OPEQ</code></a>: </b> compares for equality (<code>==</code>)</li>
-<li><b><a name="pdf-LUA_OPLT"><code>LUA_OPLT</code></a>: </b> compares for less than (<code>&lt;</code>)</li>
-<li><b><a name="pdf-LUA_OPLE"><code>LUA_OPLE</code></a>: </b> compares for less or equal (<code>&lt;=</code>)</li>
-</ul>
-<hr><h3><a name="lua_concat"><code>lua_concat</code></a></h3><p>
-<span class="apii">[-n, +1, <em>e</em>]</span>
-<pre>void lua_concat (lua_State *L, int n);</pre>
-<p>
-Concatenates the <code>n</code> values at the top of the stack,
-pops them, and leaves the result at the top.
-If <code>n</code>&nbsp;is&nbsp;1, the result is the single value on the stack
-(that is, the function does nothing);
-if <code>n</code> is 0, the result is the empty string.
-Concatenation is performed following the usual semantics of Lua
-(see <a href="#3.4.6">&sect;3.4.6</a>).
-<hr><h3><a name="lua_copy"><code>lua_copy</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void lua_copy (lua_State *L, int fromidx, int toidx);</pre>
-<p>
-Copies the element at index <code>fromidx</code>
-into the valid index <code>toidx</code>,
-replacing the value at that position.
-Values at other positions are not affected.
-<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,
-int strip);</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>
-If <code>strip</code> is true,
-the binary representation is created without debug information
-about the function.
-<p>
-The value returned is the error code returned by the last
-call to the writer;
-0&nbsp;means no errors.
-<p>
-This function does not pop the Lua function from the stack.
-<hr><h3><a name="lua_error"><code>lua_error</code></a></h3><p>
-<span class="apii">[-1, +0, <em>v</em>]</span>
-<pre>int lua_error (lua_State *L);</pre>
-<p>
-Generates a Lua error,
-using the value at the top of the stack as the error object.
-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.
-</li>
-<li><b><code>LUA_GCSETPAUSE</code>: </b>
-sets <code>data</code> as the new value
-for the <em>pause</em> of the collector (see <a href="#2.5">&sect;2.5</a>)
-and returns the previous value of the pause.
-</li>
-<li><b><code>LUA_GCSETSTEPMUL</code>: </b>
-sets <code>data</code> as the new value for the <em>step multiplier</em> of
-the collector (see <a href="#2.5">&sect;2.5</a>)
-and 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>
-</ul>
-<p>
-For more details about these options,
-see <a href="#pdf-collectgarbage"><code>collectgarbage</code></a>.
-<hr><h3><a name="lua_getallocf"><code>lua_getallocf</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_Alloc lua_getallocf (lua_State *L, void **ud);</pre>
-<p>
-Returns the memory-allocation function of a given state.
-If <code>ud</code> is not <code>NULL</code>, Lua stores in <code>*ud</code> the
-opaque pointer given when the memory-allocator function was set.
-<hr><h3><a name="lua_getfield"><code>lua_getfield</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>int lua_getfield (lua_State *L, int index, const char *k);</pre>
-<p>
-Pushes onto the stack the value <code>t[k]</code>,
-where <code>t</code> is the value at the given index.
-As in Lua, this function may trigger a metamethod
-for the "index" event (see <a href="#2.4">&sect;2.4</a>).
-<p>
-Returns the type of the pushed value.
-<hr><h3><a name="lua_getextraspace"><code>lua_getextraspace</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void *lua_getextraspace (lua_State *L);</pre>
-<p>
-Returns a pointer to a raw memory area associated with the
-given Lua state.
-The application can use this area for any purpose;
-Lua does not use it for anything.
-<p>
-Each new thread has this area initialized with a copy
-of the area of the main thread.
-<p>
-By default, this area has the size of a pointer to void,
-but you can recompile Lua with a different size for this area.
-(See <code>LUA_EXTRASPACE</code> in <code>luaconf.h</code>.)
-<hr><h3><a name="lua_getglobal"><code>lua_getglobal</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>int lua_getglobal (lua_State *L, const char *name);</pre>
-<p>
-Pushes onto the stack the value of the global <code>name</code>.
-Returns the type of that value.
-<hr><h3><a name="lua_geti"><code>lua_geti</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>int lua_geti (lua_State *L, int index, lua_Integer i);</pre>
-<p>
-Pushes onto the stack the value <code>t[i]</code>,
-where <code>t</code> is the value at the given index.
-As in Lua, this function may trigger a metamethod
-for the "index" event (see <a href="#2.4">&sect;2.4</a>).
-<p>
-Returns the type of the pushed value.
-<hr><h3><a name="lua_getmetatable"><code>lua_getmetatable</code></a></h3><p>
-<span class="apii">[-0, +(0|1), &ndash;]</span>
-<pre>int lua_getmetatable (lua_State *L, int index);</pre>
-<p>
-If the value at the given index has a metatable,
-the function pushes that metatable onto the stack and returns&nbsp;1.
-Otherwise,
-the function returns&nbsp;0 and pushes nothing on the stack.
-<hr><h3><a name="lua_gettable"><code>lua_gettable</code></a></h3><p>
-<span class="apii">[-1, +1, <em>e</em>]</span>
-<pre>int 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,
-pushing the resulting value in its place.
-As in Lua, this function may trigger a metamethod
-for the "index" event (see <a href="#2.4">&sect;2.4</a>).
-<p>
-Returns the type of the pushed value.
-<hr><h3><a name="lua_gettop"><code>lua_gettop</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_gettop (lua_State *L);</pre>
-<p>
-Returns the index of the top element in the stack.
-Because indices start at&nbsp;1,
-this result is equal to the number of elements in the stack;
-in particular, 0&nbsp;means an empty stack.
-<hr><h3><a name="lua_getuservalue"><code>lua_getuservalue</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>int lua_getuservalue (lua_State *L, int index);</pre>
-<p>
-Pushes onto the stack the Lua value associated with the userdata
-at the given index.
-<p>
-Returns the type of the pushed value.
-<hr><h3><a name="lua_insert"><code>lua_insert</code></a></h3><p>
-<span class="apii">[-1, +1, &ndash;]</span>
-<pre>void lua_insert (lua_State *L, int index);</pre>
-<p>
-Moves the top element into the given valid index,
-shifting up the elements above this index to open space.
-This function cannot be called with a pseudo-index,
-because a pseudo-index is not an actual stack position.
-<hr><h3><a name="lua_Integer"><code>lua_Integer</code></a></h3>
-<pre>typedef ... lua_Integer;</pre>
-<p>
-The type of integers in Lua.
-<p>
-By default this type is <code>long long</code>,
-(usually a 64-bit two-complement integer),
-but that can be changed to <code>long</code> or <code>int</code>
-(usually a 32-bit two-complement integer).
-(See <code>LUA_INT</code> in <code>luaconf.h</code>.)
-<p>
-Lua also defines the constants
-<a name="pdf-LUA_MININTEGER"><code>LUA_MININTEGER</code></a> and <a name="pdf-LUA_MAXINTEGER"><code>LUA_MAXINTEGER</code></a>,
-with the minimum and the maximum values that fit in this type.
-<hr><h3><a name="lua_isboolean"><code>lua_isboolean</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isboolean (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a boolean,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_iscfunction"><code>lua_iscfunction</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_iscfunction (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a C&nbsp;function,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isfunction"><code>lua_isfunction</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isfunction (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a function
-(either C or Lua), and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isinteger"><code>lua_isinteger</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isinteger (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is an integer
-(that is, the value is a number and is represented as an integer),
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_islightuserdata"><code>lua_islightuserdata</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_islightuserdata (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a light userdata,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isnil"><code>lua_isnil</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isnil (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is <b>nil</b>,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isnone"><code>lua_isnone</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isnone (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the given index is not valid,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isnoneornil"><code>lua_isnoneornil</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isnoneornil (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the given index is not valid
-or if the value at this index is <b>nil</b>,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isnumber"><code>lua_isnumber</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isnumber (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a number
-or a string convertible to a number,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isstring"><code>lua_isstring</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isstring (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a string
-or a number (which is always convertible to a string),
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_istable"><code>lua_istable</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_istable (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a table,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isthread"><code>lua_isthread</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isthread (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a thread,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isuserdata"><code>lua_isuserdata</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isuserdata (lua_State *L, int index);</pre>
-<p>
-Returns 1 if the value at the given index is a userdata
-(either full or light), and 0&nbsp;otherwise.
-<hr><h3><a name="lua_isyieldable"><code>lua_isyieldable</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_isyieldable (lua_State *L);</pre>
-<p>
-Returns 1 if the given coroutine can yield,
-and 0&nbsp;otherwise.
-<hr><h3><a name="lua_KContext"><code>lua_KContext</code></a></h3>
-<pre>typedef ... lua_KContext;</pre>
-<p>
-The type for continuation-function contexts.
-It must be a numerical type.
-This type is defined as <code>intptr_t</code>
-when <code>intptr_t</code> is available,
-so that it can store pointers too.
-Otherwise, it is defined as <code>ptrdiff_t</code>.
-<hr><h3><a name="lua_KFunction"><code>lua_KFunction</code></a></h3>
-<pre>typedef int (*lua_KFunction) (lua_State *L, int status, lua_KContext ctx);</pre>
-<p>
-Type for continuation functions (see <a href="#4.7">&sect;4.7</a>).
-<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="#3.4.7">&sect;3.4.7</a>) and
-may trigger a metamethod for the "length" event (see <a href="#2.4">&sect;2.4</a>).
-The result is pushed on the stack.
-<hr><h3><a name="lua_load"><code>lua_load</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>int lua_load (lua_State *L,
-lua_Reader reader,
-void *data,
-const char *chunkname,
-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>chunkname</code> argument gives a name to the chunk,
-which is used for error messages and in debug information (see <a href="#4.9">&sect;4.9</a>).
-<p>
-<code>lua_load</code> automatically detects whether the chunk is text or binary
-and loads it accordingly (see program <code>luac</code>).
-The string <code>mode</code> works as in function <a href="#pdf-load"><code>load</code></a>,
-with the addition that
-a <code>NULL</code> value is equivalent to the string "<code>bt</code>".
-<p>
-<code>lua_load</code> uses the stack internally,
-so the reader function must always leave the stack
-unmodified when returning.
-<p>
-If the resulting function has upvalues,
-its first upvalue is set to the value of the global environment
-stored at index <code>LUA_RIDX_GLOBALS</code> in the registry (see <a href="#4.5">&sect;4.5</a>).
-When loading main chunks,
-this upvalue will be the <code>_ENV</code> variable (see <a href="#2.2">&sect;2.2</a>).
-Other upvalues are initialized with <b>nil</b>.
-<hr><h3><a name="lua_newstate"><code>lua_newstate</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_State *lua_newstate (lua_Alloc f, void *ud);</pre>
-<p>
-Creates a new thread running in a new, independent state.
-Returns <code>NULL</code> if it cannot create the thread or the state
-(due to lack of memory).
-The argument <code>f</code> is the allocator function;
-Lua does all memory allocation for this state through this function.
-The second argument, <code>ud</code>, is an opaque pointer that Lua
-passes to the allocator in every call.
-<hr><h3><a name="lua_newtable"><code>lua_newtable</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void lua_newtable (lua_State *L);</pre>
-<p>
-Creates a new empty table and pushes it onto the stack.
-It is equivalent to <code>lua_createtable(L, 0, 0)</code>.
-<hr><h3><a name="lua_newthread"><code>lua_newthread</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>lua_State *lua_newthread (lua_State *L);</pre>
-<p>
-Creates a new thread, pushes it on the stack,
-and returns a pointer to a <a href="#lua_State"><code>lua_State</code></a> that represents this new thread.
-The new thread returned by this function shares with the original thread
-its global environment,
-but has an independent execution stack.
-<p>
-There is no explicit function to close or to destroy a thread.
-Threads are subject to garbage collection,
-like any Lua object.
-<hr><h3><a name="lua_newuserdata"><code>lua_newuserdata</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void *lua_newuserdata (lua_State *L, size_t size);</pre>
-<p>
-This function allocates a new block of memory with the given size,
-pushes onto the stack a new full userdata with the block address,
-and returns this address.
-The host program can freely use this memory.
-<hr><h3><a name="lua_next"><code>lua_next</code></a></h3><p>
-<span class="apii">[-1, +(2|0), <em>e</em>]</span>
-<pre>int lua_next (lua_State *L, int index);</pre>
-<p>
-Pops a key from the stack,
-and pushes a key&ndash;value pair from the table at the given index
-(the "next" pair after the given key).
-If there are no more elements in the table,
-then <a href="#lua_next"><code>lua_next</code></a> returns 0 (and pushes nothing).
-<p>
-A typical traversal looks like this:
-<pre>
-/* table is in the stack at index 't' */
-lua_pushnil(L);  /* first key */
-while (lua_next(L, t) != 0) {
-/* uses 'key' (at index -2) and 'value' (at index -1) */
-printf("%s - %s\n",
-lua_typename(L, lua_type(L, -2)),
-lua_typename(L, lua_type(L, -1)));
-/* removes 'value'; keeps 'key' for next iteration */
-lua_pop(L, 1);
-}
-</pre>
-<p>
-While traversing a table,
-do not call <a href="#lua_tolstring"><code>lua_tolstring</code></a> directly on a key,
-unless you know that the key is actually a string.
-Recall that <a href="#lua_tolstring"><code>lua_tolstring</code></a> may change
-the value at the given index;
-this confuses the next call to <a href="#lua_next"><code>lua_next</code></a>.
-<p>
-See function <a href="#pdf-next"><code>next</code></a> for the caveats of modifying
-the table during its traversal.
-<hr><h3><a name="lua_Number"><code>lua_Number</code></a></h3>
-<pre>typedef double lua_Number;</pre>
-<p>
-The type of floats in Lua.
-<p>
-By default this type is double,
-but that can be changed to a single float.
-(See <code>LUA_REAL</code> in <code>luaconf.h</code>.)
-<hr><h3><a name="lua_numbertointeger"><code>lua_numbertointeger</code></a></h3>
-<pre>int lua_numbertointeger (lua_Number n, lua_Integer *p);</pre>
-<p>
-Converts a Lua float to a Lua integer.
-This macro assumes that <code>n</code> has an integral value.
-If that value is within the range of Lua integers,
-it is converted to an integer and assigned to <code>*p</code>.
-The macro results in a boolean indicating whether the
-conversion was successful.
-(Note that this range test can be tricky to do
-correctly without this macro,
-due to roundings.)
-<p>
-This macro may evaluate its arguments more than once.
-<hr><h3><a name="lua_pcall"><code>lua_pcall</code></a></h3><p>
-<span class="apii">[-(nargs + 1), +(nresults|1), &ndash;]</span>
-<pre>int lua_pcall (lua_State *L, int nargs, int nresults, int msgh);</pre>
-<p>
-Calls a function in protected mode.
-<p>
-Both <code>nargs</code> and <code>nresults</code> have the same meaning as
-in <a href="#lua_call"><code>lua_call</code></a>.
-If there are no errors during the call,
-<a href="#lua_pcall"><code>lua_pcall</code></a> behaves exactly like <a href="#lua_call"><code>lua_call</code></a>.
-However, if there is any error,
-<a href="#lua_pcall"><code>lua_pcall</code></a> catches it,
-pushes a single value on the stack (the error message),
-and returns an error code.
-Like <a href="#lua_call"><code>lua_call</code></a>,
-<a href="#lua_pcall"><code>lua_pcall</code></a> always removes the function
-and its arguments from the stack.
-<p>
-If <code>msgh</code> is 0,
-then the error message returned on the stack
-is exactly the original error message.
-Otherwise, <code>msgh</code> is the stack index of a
-<em>message handler</em>.
-(In the current implementation, this index cannot be a pseudo-index.)
-In case of runtime errors,
-this function will be called with the error message
-and its return value will be the message
-returned on the stack by <a href="#lua_pcall"><code>lua_pcall</code></a>.
-<p>
-Typically, the message handler is used to add more debug
-information to the error message, such as a stack traceback.
-Such information cannot be gathered after the return of <a href="#lua_pcall"><code>lua_pcall</code></a>,
-since by then the stack has unwound.
-<p>
-The <a href="#lua_pcall"><code>lua_pcall</code></a> function returns one of the following constants
-(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.)
-</li>
-</ul>
-<hr><h3><a name="lua_pcallk"><code>lua_pcallk</code></a></h3><p>
-<span class="apii">[-(nargs + 1), +(nresults|1), &ndash;]</span>
-<pre>int lua_pcallk (lua_State *L,
-int nargs,
-int nresults,
-int msgh,
-lua_KContext ctx,
-lua_KFunction k);</pre>
-<p>
-This function behaves exactly like <a href="#lua_pcall"><code>lua_pcall</code></a>,
-but allows the called function to yield (see <a href="#4.7">&sect;4.7</a>).
-<hr><h3><a name="lua_pop"><code>lua_pop</code></a></h3><p>
-<span class="apii">[-n, +0, &ndash;]</span>
-<pre>void lua_pop (lua_State *L, int n);</pre>
-<p>
-Pops <code>n</code> elements from the stack.
-<hr><h3><a name="lua_pushboolean"><code>lua_pushboolean</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushboolean (lua_State *L, int b);</pre>
-<p>
-Pushes a boolean value with value <code>b</code> onto the stack.
-<hr><h3><a name="lua_pushcclosure"><code>lua_pushcclosure</code></a></h3><p>
-<span class="apii">[-n, +1, <em>e</em>]</span>
-<pre>void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n);</pre>
-<p>
-Pushes a new C&nbsp;closure onto the stack.
-<p>
-When a C&nbsp;function is created,
-it is possible to associate some values with it,
-thus creating a C&nbsp;closure (see <a href="#4.4">&sect;4.4</a>);
-these values are then accessible to the function whenever it is called.
-To associate values with a C&nbsp;function,
-first these values must be pushed onto the stack
-(when there are multiple values, the first value is pushed first).
-Then <a href="#lua_pushcclosure"><code>lua_pushcclosure</code></a>
-is called to create and push the C&nbsp;function onto the stack,
-with the argument <code>n</code> telling how many values will be
-associated with the function.
-<a href="#lua_pushcclosure"><code>lua_pushcclosure</code></a> also pops these values from the stack.
-<p>
-The maximum value for <code>n</code> is 255.
-<p>
-When <code>n</code> is zero,
-this function creates a <em>light C function</em>,
-which is just a pointer to the C&nbsp;function.
-In that case, it never raises a memory error.
-<hr><h3><a name="lua_pushcfunction"><code>lua_pushcfunction</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushcfunction (lua_State *L, lua_CFunction f);</pre>
-<p>
-Pushes a C&nbsp;function onto the stack.
-This function receives a pointer to a C function
-and pushes onto the stack a Lua value of type <code>function</code> that,
-when called, invokes the corresponding C&nbsp;function.
-<p>
-Any function to be registered in Lua must
-follow the correct protocol to receive its parameters
-and return its results (see <a href="#lua_CFunction"><code>lua_CFunction</code></a>).
-<p>
-<code>lua_pushcfunction</code> is defined as a macro:
-<pre>
-#define lua_pushcfunction(L,f)  lua_pushcclosure(L,f,0)
-</pre><p>
-Note that <code>f</code> is used twice.
-<hr><h3><a name="lua_pushfstring"><code>lua_pushfstring</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>const char *lua_pushfstring (lua_State *L, const char *fmt, ...);</pre>
-<p>
-Pushes onto the stack a formatted string
-and returns a pointer to this string.
-It is similar to the ISO&nbsp;C function <code>sprintf</code>,
-but has some important differences:
-<ul>
-<li>
-You do not have to allocate space for the result:
-the result is a Lua string and Lua takes care of memory allocation
-(and deallocation, through garbage collection).
-</li>
-<li>
-The conversion specifiers are quite restricted.
-There are no flags, widths, or precisions.
-The conversion specifiers can only be
-'<code>%%</code>' (inserts the character '<code>%</code>'),
-'<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>%L</code>' (inserts a <a href="#lua_Integer"><code>lua_Integer</code></a>),
-'<code>%p</code>' (inserts a pointer as a hexadecimal numeral),
-'<code>%d</code>' (inserts an <code>int</code>),
-'<code>%c</code>' (inserts an <code>int</code> as a one-byte character), and
-'<code>%U</code>' (inserts a <code>long int</code> as a UTF-8 byte sequence).
-</li>
-</ul>
-<hr><h3><a name="lua_pushglobaltable"><code>lua_pushglobaltable</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushglobaltable (lua_State *L);</pre>
-<p>
-Pushes the global environment onto the stack.
-<hr><h3><a name="lua_pushinteger"><code>lua_pushinteger</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushinteger (lua_State *L, lua_Integer n);</pre>
-<p>
-Pushes an integer with value <code>n</code> onto the stack.
-<hr><h3><a name="lua_pushlightuserdata"><code>lua_pushlightuserdata</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushlightuserdata (lua_State *L, void *p);</pre>
-<p>
-Pushes a light userdata onto the stack.
-<p>
-Userdata represent C&nbsp;values in Lua.
-A <em>light userdata</em> represents a pointer, a <code>void*</code>.
-It is a value (like a number):
-you do not create it, it has no individual metatable,
-and it is not collected (as it was never created).
-A light userdata is equal to "any"
-light userdata with the same C&nbsp;address.
-<hr><h3><a name="lua_pushliteral"><code>lua_pushliteral</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>const char *lua_pushliteral (lua_State *L, const char *s);</pre>
-<p>
-This macro is equivalent to <a href="#lua_pushlstring"><code>lua_pushlstring</code></a>,
-but can be used only when <code>s</code> is a literal string.
-It automatically provides the string length.
-<hr><h3><a name="lua_pushlstring"><code>lua_pushlstring</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>const char *lua_pushlstring (lua_State *L, const char *s, size_t len);</pre>
-<p>
-Pushes the string pointed to by <code>s</code> with size <code>len</code>
-onto the stack.
-Lua makes (or reuses) an internal copy of the given string,
-so the memory at <code>s</code> can be freed or reused immediately after
-the function returns.
-The string can contain any binary data,
-including embedded zeros.
-<p>
-Returns a pointer to the internal copy of the string.
-<hr><h3><a name="lua_pushnil"><code>lua_pushnil</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushnil (lua_State *L);</pre>
-<p>
-Pushes a nil value onto the stack.
-<hr><h3><a name="lua_pushnumber"><code>lua_pushnumber</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushnumber (lua_State *L, lua_Number n);</pre>
-<p>
-Pushes a float with value <code>n</code> onto the stack.
-<hr><h3><a name="lua_pushstring"><code>lua_pushstring</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>const char *lua_pushstring (lua_State *L, const char *s);</pre>
-<p>
-Pushes the zero-terminated string pointed to by <code>s</code>
-onto the stack.
-Lua makes (or reuses) an internal copy of the given string,
-so the memory at <code>s</code> can be freed or reused immediately after
-the function returns.
-<p>
-Returns a pointer to the internal copy of the string.
-<p>
-If <code>s</code> is <code>NULL</code>, pushes <b>nil</b> and returns <code>NULL</code>.
-<hr><h3><a name="lua_pushthread"><code>lua_pushthread</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>int lua_pushthread (lua_State *L);</pre>
-<p>
-Pushes the thread represented by <code>L</code> onto the stack.
-Returns 1 if this thread is the main thread of its state.
-<hr><h3><a name="lua_pushvalue"><code>lua_pushvalue</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>void lua_pushvalue (lua_State *L, int index);</pre>
-<p>
-Pushes a copy of the element at the given index
-onto the stack.
-<hr><h3><a name="lua_pushvfstring"><code>lua_pushvfstring</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>const char *lua_pushvfstring (lua_State *L,
-const char *fmt,
-va_list argp);</pre>
-<p>
-Equivalent to <a href="#lua_pushfstring"><code>lua_pushfstring</code></a>, except that it receives a <code>va_list</code>
-instead of a variable number of arguments.
-<hr><h3><a name="lua_rawequal"><code>lua_rawequal</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_rawequal (lua_State *L, int index1, int index2);</pre>
-<p>
-Returns 1 if the two values in indices <code>index1</code> and
-<code>index2</code> are primitively equal
-(that is, without calling metamethods).
-Otherwise returns&nbsp;0.
-Also returns&nbsp;0 if any of the indices are not valid.
-<hr><h3><a name="lua_rawget"><code>lua_rawget</code></a></h3><p>
-<span class="apii">[-1, +1, &ndash;]</span>
-<pre>int lua_rawget (lua_State *L, int index);</pre>
-<p>
-Similar to <a href="#lua_gettable"><code>lua_gettable</code></a>, but does a raw access
-(i.e., without metamethods).
-<hr><h3><a name="lua_rawgeti"><code>lua_rawgeti</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>int lua_rawgeti (lua_State *L, int index, lua_Integer 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.
-<p>
-Returns the type of the pushed value.
-<hr><h3><a name="lua_rawgetp"><code>lua_rawgetp</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>int 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.
-<p>
-Returns the type of the pushed value.
-<hr><h3><a name="lua_rawlen"><code>lua_rawlen</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>size_t lua_rawlen (lua_State *L, int index);</pre>
-<p>
-Returns the raw "length" of the value at the given index:
-for strings, this is the string length;
-for tables, this is the result of the length operator ('<code>#</code>')
-with no metamethods;
-for userdata, this is the size of the block of memory allocated
-for the userdata;
-for other values, it is&nbsp;0.
-<hr><h3><a name="lua_rawset"><code>lua_rawset</code></a></h3><p>
-<span class="apii">[-2, +0, <em>e</em>]</span>
-<pre>void lua_rawset (lua_State *L, int index);</pre>
-<p>
-Similar to <a href="#lua_settable"><code>lua_settable</code></a>, but does a raw assignment
-(i.e., without metamethods).
-<hr><h3><a name="lua_rawseti"><code>lua_rawseti</code></a></h3><p>
-<span class="apii">[-1, +0, <em>e</em>]</span>
-<pre>void lua_rawseti (lua_State *L, int index, lua_Integer i);</pre>
-<p>
-Does the equivalent of <code>t[i] = v</code>,
-where <code>t</code> is the table at the given index
-and <code>v</code> is the value at the top of the stack.
-<p>
-This function pops the value from the stack.
-The assignment is raw;
-that is, it does not invoke metamethods.
-<hr><h3><a name="lua_rawsetp"><code>lua_rawsetp</code></a></h3><p>
-<span class="apii">[-1, +0, <em>e</em>]</span>
-<pre>void lua_rawsetp (lua_State *L, int index, const void *p);</pre>
-<p>
-Does the equivalent of <code>t[k] = v</code>,
-where <code>t</code> is the table at the given index,
-<code>k</code> is the pointer <code>p</code> represented as a light userdata,
-and <code>v</code> is the value at the top of the stack.
-<p>
-This function pops the value from the stack.
-The assignment is raw;
-that is, it does not invoke metamethods.
-<hr><h3><a name="lua_Reader"><code>lua_Reader</code></a></h3>
-<pre>typedef const char * (*lua_Reader) (lua_State *L,
-void *data,
-size_t *size);</pre>
-<p>
-The reader function used by <a href="#lua_load"><code>lua_load</code></a>.
-Every time it needs another piece of the chunk,
-<a href="#lua_load"><code>lua_load</code></a> calls the reader,
-passing along its <code>data</code> parameter.
-The reader must return a pointer to a block of memory
-with a new piece of the chunk
-and set <code>size</code> to the block size.
-The block must exist until the reader function is called again.
-To signal the end of the chunk,
-the reader must return <code>NULL</code> or set <code>size</code> to zero.
-The reader function may return pieces of any size greater than zero.
-<hr><h3><a name="lua_register"><code>lua_register</code></a></h3><p>
-<span class="apii">[-0, +0, <em>e</em>]</span>
-<pre>void lua_register (lua_State *L, const char *name, lua_CFunction f);</pre>
-<p>
-Sets the C function <code>f</code> as the new value of global <code>name</code>.
-It is defined as a macro:
-<pre>
-#define lua_register(L,n,f) \
-(lua_pushcfunction(L, f), lua_setglobal(L, n))
-</pre>
-<hr><h3><a name="lua_remove"><code>lua_remove</code></a></h3><p>
-<span class="apii">[-1, +0, &ndash;]</span>
-<pre>void lua_remove (lua_State *L, int index);</pre>
-<p>
-Removes the element at the given valid index,
-shifting down the elements above this index to fill the gap.
-This function cannot be called with a pseudo-index,
-because a pseudo-index is not an actual stack position.
-<hr><h3><a name="lua_replace"><code>lua_replace</code></a></h3><p>
-<span class="apii">[-1, +0, &ndash;]</span>
-<pre>void lua_replace (lua_State *L, int index);</pre>
-<p>
-Moves the top element into the given valid index
-without shifting any element
-(therefore replacing the value at the given index),
-and then pops the top element.
-<hr><h3><a name="lua_resume"><code>lua_resume</code></a></h3><p>
-<span class="apii">[-?, +?, &ndash;]</span>
-<pre>int lua_resume (lua_State *L, lua_State *from, int nargs);</pre>
-<p>
-Starts and resumes a coroutine in a given thread.
-<p>
-To start a coroutine,
-you push onto the thread stack the main function plus any arguments;
-then you call <a href="#lua_resume"><code>lua_resume</code></a>,
-with <code>nargs</code> being the number of arguments.
-This call returns when the coroutine suspends or finishes its execution.
-When it returns, the stack contains all values passed to <a href="#lua_yield"><code>lua_yield</code></a>,
-or all values returned by the body function.
-<a href="#lua_resume"><code>lua_resume</code></a> returns
-<a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a> if the coroutine yields,
-<a href="#pdf-LUA_OK"><code>LUA_OK</code></a> if the coroutine finishes its execution
-without errors,
-or an error code in case of errors (see <a href="#lua_pcall"><code>lua_pcall</code></a>).
-<p>
-In case of errors,
-the stack is not unwound,
-so you can use the debug API over it.
-The error message is on the top of the stack.
-<p>
-To resume a coroutine,
-you remove any results from the last <a href="#lua_yield"><code>lua_yield</code></a>,
-put on its stack only the values to
-be passed as results from <code>yield</code>,
-and then call <a href="#lua_resume"><code>lua_resume</code></a>.
-<p>
-The parameter <code>from</code> represents the coroutine that is resuming <code>L</code>.
-If there is no such coroutine,
-this parameter can be <code>NULL</code>.
-<hr><h3><a name="lua_rotate"><code>lua_rotate</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void lua_rotate (lua_State *L, int idx, int n);</pre>
-<p>
-Rotates the stack elements from <code>idx</code> to the top <code>n</code> positions
-in the direction of the top, for a positive <code>n</code>,
-or <code>-n</code> positions in the direction of the bottom,
-for a negative <code>n</code>.
-The absolute value of <code>n</code> must not be greater than the size
-of the slice being rotated.
-<hr><h3><a name="lua_setallocf"><code>lua_setallocf</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void lua_setallocf (lua_State *L, lua_Alloc f, void *ud);</pre>
-<p>
-Changes the allocator function of a given state to <code>f</code>
-with user data <code>ud</code>.
-<hr><h3><a name="lua_setfield"><code>lua_setfield</code></a></h3><p>
-<span class="apii">[-1, +0, <em>e</em>]</span>
-<pre>void lua_setfield (lua_State *L, int index, const char *k);</pre>
-<p>
-Does the equivalent to <code>t[k] = v</code>,
-where <code>t</code> is the value at the given index
-and <code>v</code> is the value at the top of the stack.
-<p>
-This function pops the value from the stack.
-As in Lua, this function may trigger a metamethod
-for the "newindex" event (see <a href="#2.4">&sect;2.4</a>).
-<hr><h3><a name="lua_setglobal"><code>lua_setglobal</code></a></h3><p>
-<span class="apii">[-1, +0, <em>e</em>]</span>
-<pre>void lua_setglobal (lua_State *L, const char *name);</pre>
-<p>
-Pops a value from the stack and
-sets it as the new value of global <code>name</code>.
-<hr><h3><a name="lua_seti"><code>lua_seti</code></a></h3><p>
-<span class="apii">[-1, +0, <em>e</em>]</span>
-<pre>void lua_seti (lua_State *L, int index, lua_Integer n);</pre>
-<p>
-Does the equivalent to <code>t[n] = v</code>,
-where <code>t</code> is the value at the given index
-and <code>v</code> is the value at the top of the stack.
-<p>
-This function pops the value from the stack.
-As in Lua, this function may trigger a metamethod
-for the "newindex" event (see <a href="#2.4">&sect;2.4</a>).
-<hr><h3><a name="lua_setmetatable"><code>lua_setmetatable</code></a></h3><p>
-<span class="apii">[-1, +0, &ndash;]</span>
-<pre>void lua_setmetatable (lua_State *L, int index);</pre>
-<p>
-Pops a table from the stack and
-sets it as the new metatable for the value at the given index.
-<hr><h3><a name="lua_settable"><code>lua_settable</code></a></h3><p>
-<span class="apii">[-2, +0, <em>e</em>]</span>
-<pre>void lua_settable (lua_State *L, int index);</pre>
-<p>
-Does the equivalent to <code>t[k] = v</code>,
-where <code>t</code> is the value at the given index,
-<code>v</code> is the value at the top of the stack,
-and <code>k</code> is the value just below the top.
-<p>
-This function pops both the key and the value from the stack.
-As in Lua, this function may trigger a metamethod
-for the "newindex" event (see <a href="#2.4">&sect;2.4</a>).
-<hr><h3><a name="lua_settop"><code>lua_settop</code></a></h3><p>
-<span class="apii">[-?, +?, &ndash;]</span>
-<pre>void lua_settop (lua_State *L, int index);</pre>
-<p>
-Accepts any index, or&nbsp;0,
-and sets the stack top to this index.
-If the new top is larger than the old one,
-then the new elements are filled with <b>nil</b>.
-If <code>index</code> is&nbsp;0, then all stack elements are removed.
-<hr><h3><a name="lua_setuservalue"><code>lua_setuservalue</code></a></h3><p>
-<span class="apii">[-1, +0, &ndash;]</span>
-<pre>void lua_setuservalue (lua_State *L, int index);</pre>
-<p>
-Pops a value from the stack and sets it as
-the new value associated to the userdata at the given index.
-<hr><h3><a name="lua_State"><code>lua_State</code></a></h3>
-<pre>typedef struct lua_State lua_State;</pre>
-<p>
-An opaque structure that points to a thread and indirectly
-(through the thread) to the whole state of a Lua interpreter.
-The Lua library is fully reentrant:
-it has no global variables.
-All information about a state is accessible through this structure.
-<p>
-A pointer to this structure must be passed as the first argument to
-every function in the library, except to <a href="#lua_newstate"><code>lua_newstate</code></a>,
-which creates a Lua state from scratch.
-<hr><h3><a name="lua_status"><code>lua_status</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_status (lua_State *L);</pre>
-<p>
-Returns the status of the thread <code>L</code>.
-<p>
-The status can be 0 (<a href="#pdf-LUA_OK"><code>LUA_OK</code></a>) for a normal thread,
-an error code if the thread finished the execution
-of a <a href="#lua_resume"><code>lua_resume</code></a> with an error,
-or <a name="pdf-LUA_YIELD"><code>LUA_YIELD</code></a> if the thread is suspended.
-<p>
-You can only call functions in threads with status <a href="#pdf-LUA_OK"><code>LUA_OK</code></a>.
-You can resume threads with status <a href="#pdf-LUA_OK"><code>LUA_OK</code></a>
-(to start a new coroutine) or <a href="#pdf-LUA_YIELD"><code>LUA_YIELD</code></a>
-(to resume a coroutine).
-<hr><h3><a name="lua_stringtonumber"><code>lua_stringtonumber</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>size_t lua_stringtonumber (lua_State *L, const char *s);</pre>
-<p>
-Converts the zero-terminated string <code>s</code> to a number,
-pushes that number into the stack,
-and returns the total size of the string,
-that is, its length plus one.
-The conversion can result in an integer or a float,
-according to the lexical conventions of Lua (see <a href="#3.1">&sect;3.1</a>).
-The string may have leading and trailing spaces and a sign.
-If the string is not a valid numeral,
-returns 0 and pushes nothing.
-(Note that the result can be used as a boolean,
-true if the conversion succeeds.)
-<hr><h3><a name="lua_toboolean"><code>lua_toboolean</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_toboolean (lua_State *L, int index);</pre>
-<p>
-Converts the Lua value at the given index to a C&nbsp;boolean
-value (0&nbsp;or&nbsp;1).
-Like all tests in Lua,
-<a href="#lua_toboolean"><code>lua_toboolean</code></a> returns true for any Lua value
-different from <b>false</b> and <b>nil</b>;
-otherwise it returns false.
-(If you want to accept only actual boolean values,
-use <a href="#lua_isboolean"><code>lua_isboolean</code></a> to test the value's type.)
-<hr><h3><a name="lua_tocfunction"><code>lua_tocfunction</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_CFunction lua_tocfunction (lua_State *L, int index);</pre>
-<p>
-Converts a value at the given index to a C&nbsp;function.
-That value must be a C&nbsp;function;
-otherwise, returns <code>NULL</code>.
-<hr><h3><a name="lua_tointeger"><code>lua_tointeger</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_Integer lua_tointeger (lua_State *L, int index);</pre>
-<p>
-Equivalent to <a href="#lua_tointegerx"><code>lua_tointegerx</code></a> with <code>isnum</code> equal to <code>NULL</code>.
-<hr><h3><a name="lua_tointegerx"><code>lua_tointegerx</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_Integer lua_tointegerx (lua_State *L, int index, int *isnum);</pre>
-<p>
-Converts the Lua value at the given index
-to the signed integral type <a href="#lua_Integer"><code>lua_Integer</code></a>.
-The Lua value must be an integer,
-or a number or string convertible to an integer (see <a href="#3.4.3">&sect;3.4.3</a>);
-otherwise, <code>lua_tointegerx</code> returns&nbsp;0.
-<p>
-If <code>isnum</code> is not <code>NULL</code>,
-its referent is assigned a boolean value that
-indicates whether the operation succeeded.
-<hr><h3><a name="lua_tolstring"><code>lua_tolstring</code></a></h3><p>
-<span class="apii">[-0, +0, <em>e</em>]</span>
-<pre>const char *lua_tolstring (lua_State *L, int index, size_t *len);</pre>
-<p>
-Converts the Lua value at the given index to a C&nbsp;string.
-If <code>len</code> is not <code>NULL</code>,
-it also sets <code>*len</code> with the string length.
-The Lua value must be a string or a number;
-otherwise, the function returns <code>NULL</code>.
-If the value is a number,
-then <code>lua_tolstring</code> also
-<em>changes the actual value in the stack to a string</em>.
-(This change confuses <a href="#lua_next"><code>lua_next</code></a>
-when <code>lua_tolstring</code> is applied to keys during a table traversal.)
-<p>
-<code>lua_tolstring</code> returns a fully aligned pointer
-to a string inside the Lua state.
-This string always has a zero ('<code>\0</code>')
-after its last character (as in&nbsp;C),
-but can contain other zeros in its body.
-<p>
-Because Lua has garbage collection,
-there is no guarantee that the pointer returned by <code>lua_tolstring</code>
-will be valid after the corresponding Lua value is removed from the stack.
-<hr><h3><a name="lua_tonumber"><code>lua_tonumber</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_Number lua_tonumber (lua_State *L, int index);</pre>
-<p>
-Equivalent to <a href="#lua_tonumberx"><code>lua_tonumberx</code></a> with <code>isnum</code> equal to <code>NULL</code>.
-<hr><h3><a name="lua_tonumberx"><code>lua_tonumberx</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_Number lua_tonumberx (lua_State *L, int index, int *isnum);</pre>
-<p>
-Converts the Lua value at the given index
-to the C&nbsp;type <a href="#lua_Number"><code>lua_Number</code></a> (see <a href="#lua_Number"><code>lua_Number</code></a>).
-The Lua value must be a number or a string convertible to a number
-(see <a href="#3.4.3">&sect;3.4.3</a>);
-otherwise, <a href="#lua_tonumberx"><code>lua_tonumberx</code></a> returns&nbsp;0.
-<p>
-If <code>isnum</code> is not <code>NULL</code>,
-its referent is assigned a boolean value that
-indicates whether the operation succeeded.
-<hr><h3><a name="lua_topointer"><code>lua_topointer</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>const void *lua_topointer (lua_State *L, int index);</pre>
-<p>
-Converts the value at the given index to a generic
-C&nbsp;pointer (<code>void*</code>).
-The value can be a userdata, a table, a thread, or a function;
-otherwise, <code>lua_topointer</code> returns <code>NULL</code>.
-Different objects will give different pointers.
-There is no way to convert the pointer back to its original value.
-<p>
-Typically this function is used only for debug information.
-<hr><h3><a name="lua_tostring"><code>lua_tostring</code></a></h3><p>
-<span class="apii">[-0, +0, <em>e</em>]</span>
-<pre>const char *lua_tostring (lua_State *L, int index);</pre>
-<p>
-Equivalent to <a href="#lua_tolstring"><code>lua_tolstring</code></a> with <code>len</code> equal to <code>NULL</code>.
-<hr><h3><a name="lua_tothread"><code>lua_tothread</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_State *lua_tothread (lua_State *L, int index);</pre>
-<p>
-Converts the value at the given index to a Lua thread
-(represented as <code>lua_State*</code>).
-This value must be a thread;
-otherwise, the function returns <code>NULL</code>.
-<hr><h3><a name="lua_touserdata"><code>lua_touserdata</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void *lua_touserdata (lua_State *L, int index);</pre>
-<p>
-If the value at the given index is a full userdata,
-returns its block address.
-If the value is a light userdata,
-returns its pointer.
-Otherwise, returns <code>NULL</code>.
-<hr><h3><a name="lua_type"><code>lua_type</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_type (lua_State *L, int index);</pre>
-<p>
-Returns the type of the value in the given valid index,
-or <code>LUA_TNONE</code> for a non-valid (but acceptable) index.
-The types returned by <a href="#lua_type"><code>lua_type</code></a> are coded by the following constants
-defined in <code>lua.h</code>:
-<a name="pdf-LUA_TNIL"><code>LUA_TNIL</code></a>,
-<a name="pdf-LUA_TNUMBER"><code>LUA_TNUMBER</code></a>,
-<a name="pdf-LUA_TBOOLEAN"><code>LUA_TBOOLEAN</code></a>,
-<a name="pdf-LUA_TSTRING"><code>LUA_TSTRING</code></a>,
-<a name="pdf-LUA_TTABLE"><code>LUA_TTABLE</code></a>,
-<a name="pdf-LUA_TFUNCTION"><code>LUA_TFUNCTION</code></a>,
-<a name="pdf-LUA_TUSERDATA"><code>LUA_TUSERDATA</code></a>,
-<a name="pdf-LUA_TTHREAD"><code>LUA_TTHREAD</code></a>,
-and
-<a name="pdf-LUA_TLIGHTUSERDATA"><code>LUA_TLIGHTUSERDATA</code></a>.
-<hr><h3><a name="lua_typename"><code>lua_typename</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>const char *lua_typename (lua_State *L, int tp);</pre>
-<p>
-Returns the name of the type encoded by the value <code>tp</code>,
-which must be one the values returned by <a href="#lua_type"><code>lua_type</code></a>.
-<hr><h3><a name="lua_Unsigned"><code>lua_Unsigned</code></a></h3>
-<pre>typedef ... lua_Unsigned;</pre>
-<p>
-The unsigned version of <a href="#lua_Integer"><code>lua_Integer</code></a>.
-<hr><h3><a name="lua_upvalueindex"><code>lua_upvalueindex</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_upvalueindex (int i);</pre>
-<p>
-Returns the pseudo-index that represents the <code>i</code>-th upvalue of
-the running function (see <a href="#4.4">&sect;4.4</a>).
-<hr><h3><a name="lua_version"><code>lua_version</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>const lua_Number *lua_version (lua_State *L);</pre>
-<p>
-Returns the address of the version number stored in the Lua core.
-When called with a valid <a href="#lua_State"><code>lua_State</code></a>,
-returns the address of the version used to create that state.
-When called with <code>NULL</code>,
-returns the address of the version running the call.
-<hr><h3><a name="lua_Writer"><code>lua_Writer</code></a></h3>
-<pre>typedef int (*lua_Writer) (lua_State *L,
-const void* p,
-size_t sz,
-void* ud);</pre>
-<p>
-The type of the writer function used by <a href="#lua_dump"><code>lua_dump</code></a>.
-Every time it produces another piece of chunk,
-<a href="#lua_dump"><code>lua_dump</code></a> calls the writer,
-passing along the buffer to be written (<code>p</code>),
-its size (<code>sz</code>),
-and the <code>data</code> parameter supplied to <a href="#lua_dump"><code>lua_dump</code></a>.
-<p>
-The writer returns an error code:
-0&nbsp;means no errors;
-any other value means an error and stops <a href="#lua_dump"><code>lua_dump</code></a> from
-calling the writer again.
-<hr><h3><a name="lua_xmove"><code>lua_xmove</code></a></h3><p>
-<span class="apii">[-?, +?, &ndash;]</span>
-<pre>void lua_xmove (lua_State *from, lua_State *to, int n);</pre>
-<p>
-Exchange values between different threads of the same state.
-<p>
-This function pops <code>n</code> values from the stack <code>from</code>,
-and pushes them onto the stack <code>to</code>.
-<hr><h3><a name="lua_yield"><code>lua_yield</code></a></h3><p>
-<span class="apii">[-?, +?, <em>e</em>]</span>
-<pre>int lua_yield (lua_State *L, int nresults);</pre>
-<p>
-This function is equivalent to <a href="#lua_yieldk"><code>lua_yieldk</code></a>,
-but it has no continuation (see <a href="#4.7">&sect;4.7</a>).
-Therefore, when the thread resumes,
-it continues 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">[-?, +?, <em>e</em>]</span>
-<pre>int lua_yieldk (lua_State *L,
-int nresults,
-lua_KContext ctx,
-lua_KFunction k);</pre>
-<p>
-Yields a coroutine (thread).
-<p>
-When a C&nbsp;function calls <a href="#lua_yieldk"><code>lua_yieldk</code></a>,
-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 will be passed as results to <a href="#lua_resume"><code>lua_resume</code></a>.
-<p>
-When the coroutine is resumed again,
-Lua calls the given continuation function <code>k</code> to continue
-the execution of the C function that yielded (see <a href="#4.7">&sect;4.7</a>).
-This continuation function receives the same stack
-from the previous function,
-with the <code>n</code> results removed and
-replaced by the arguments passed to <a href="#lua_resume"><code>lua_resume</code></a>.
-Moreover,
-the continuation function receives the value <code>ctx</code>
-that was passed to <a href="#lua_yieldk"><code>lua_yieldk</code></a>.
-<p>
-Usually, this function does not return;
-when the coroutine eventually resumes,
-it continues executing the continuation function.
-However, there is one special case,
-which is when this function is called
-from inside a line hook (see <a href="#4.9">&sect;4.9</a>).
-In that case, <code>lua_yieldk</code> should be called with no continuation
-(probably in the form of <a href="#lua_yield"><code>lua_yield</code></a>),
-and the hook should return immediately after the call.
-Lua will yield and,
-when the coroutine resumes again,
-it will continue the normal execution
-of the (Lua) function that triggered the hook.
-<p>
-This function can raise an error if it is called from a thread
-with a pending C call with no continuation function,
-or it is called from a thread that is not running inside a resume
-(e.g., the main thread).
-<h2>4.9 &ndash; <a name="4.9">The Debug Interface</a></h2>
-<p>
-Lua has no built-in debugging facilities.
-Instead, it offers a special interface
-by means of functions and <em>hooks</em>.
-This interface allows the construction of different
-kinds of debuggers, profilers, and other tools
-that need "inside information" from the interpreter.
-<hr><h3><a name="lua_Debug"><code>lua_Debug</code></a></h3>
-<pre>typedef struct lua_Debug {
-int event;
-const char *name;           /* (n) */
-const char *namewhat;       /* (n) */
-const char *what;           /* (S) */
-const char *source;         /* (S) */
-int currentline;            /* (l) */
-int linedefined;            /* (S) */
-int lastlinedefined;        /* (S) */
-unsigned char nups;         /* (u) number of upvalues */
-unsigned char nparams;      /* (u) number of parameters */
-char isvararg;              /* (u) */
-char istailcall;            /* (t) */
-char short_src[LUA_IDSIZE]; /* (S) */
-/* private part */
-<em>other fields</em>
-} lua_Debug;</pre>
-<p>
-A structure used to carry different pieces of
-information about a function or an activation record.
-<a href="#lua_getstack"><code>lua_getstack</code></a> fills only the private part
-of this structure, for later use.
-To fill the other fields of <a href="#lua_Debug"><code>lua_Debug</code></a> with useful information,
-call <a href="#lua_getinfo"><code>lua_getinfo</code></a>.
-<p>
-The fields of <a href="#lua_Debug"><code>lua_Debug</code></a> have the following meaning:
-<ul>
-<li><b><code>source</code>: </b>
-the name of the chunk that created the function.
-If <code>source</code> starts with a '<code>@</code>',
-it means that the function was defined in a file where
-the file name follows the '<code>@</code>'.
-If <code>source</code> starts with a '<code>=</code>',
-the remainder of its contents describe the source in a user-dependent manner.
-Otherwise,
-the function was defined in a string where
-<code>source</code> is that string.
-</li>
-<li><b><code>short_src</code>: </b>
-a "printable" version of <code>source</code>, to be used in error messages.
-</li>
-<li><b><code>linedefined</code>: </b>
-the line number where the definition of the function starts.
-</li>
-<li><b><code>lastlinedefined</code>: </b>
-the line number where the definition of the function ends.
-</li>
-<li><b><code>what</code>: </b>
-the string <code>"Lua"</code> if the function is a Lua function,
-<code>"C"</code> if it is a C&nbsp;function,
-<code>"main"</code> if it is the main part of a chunk.
-</li>
-<li><b><code>currentline</code>: </b>
-the current line where the given function is executing.
-When no line information is available,
-<code>currentline</code> is set to -1.
-</li>
-<li><b><code>name</code>: </b>
-a reasonable name for the given function.
-Because functions in Lua are first-class values,
-they do not have a fixed name:
-some functions can be the value of multiple global variables,
-while others can be stored only in a table field.
-The <code>lua_getinfo</code> function checks how the function was
-called to find a suitable name.
-If it cannot find a name,
-then <code>name</code> is set to <code>NULL</code>.
-</li>
-<li><b><code>namewhat</code>: </b>
-explains the <code>name</code> field.
-The value of <code>namewhat</code> can be
-<code>"global"</code>, <code>"local"</code>, <code>"method"</code>,
-<code>"field"</code>, <code>"upvalue"</code>, or <code>""</code> (the empty string),
-according to how the function was called.
-(Lua uses the empty string when no other option seems to apply.)
-</li>
-<li><b><code>istailcall</code>: </b>
-true if this function invocation was called by a tail call.
-In this case, the caller of this level is not in the stack.
-</li>
-<li><b><code>nups</code>: </b>
-the number of upvalues of the function.
-</li>
-<li><b><code>nparams</code>: </b>
-the number of fixed parameters of the function
-(always 0&nbsp;for C&nbsp;functions).
-</li>
-<li><b><code>isvararg</code>: </b>
-true if the function is a vararg function
-(always true for C&nbsp;functions).
-</li>
-</ul>
-<hr><h3><a name="lua_gethook"><code>lua_gethook</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_Hook lua_gethook (lua_State *L);</pre>
-<p>
-Returns the current hook function.
-<hr><h3><a name="lua_gethookcount"><code>lua_gethookcount</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_gethookcount (lua_State *L);</pre>
-<p>
-Returns the current hook count.
-<hr><h3><a name="lua_gethookmask"><code>lua_gethookmask</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_gethookmask (lua_State *L);</pre>
-<p>
-Returns the current hook mask.
-<hr><h3><a name="lua_getinfo"><code>lua_getinfo</code></a></h3><p>
-<span class="apii">[-(0|1), +(0|1|2), <em>e</em>]</span>
-<pre>int lua_getinfo (lua_State *L, const char *what, lua_Debug *ar);</pre>
-<p>
-Gets information about a specific function or function invocation.
-<p>
-To get information about a function invocation,
-the parameter <code>ar</code> must be a valid activation record that was
-filled by a previous call to <a href="#lua_getstack"><code>lua_getstack</code></a> or
-given as argument to a hook (see <a href="#lua_Hook"><code>lua_Hook</code></a>).
-<p>
-To get information about a function you push it onto the stack
-and start the <code>what</code> string with the character '<code>&gt;</code>'.
-(In that case,
-<code>lua_getinfo</code> pops the function from the top of the stack.)
-For instance, to know in which line a function <code>f</code> was defined,
-you can write the following code:
-<pre>
-lua_Debug ar;
-lua_getglobal(L, "f");  /* get global 'f' */
-lua_getinfo(L, "&gt;S", &amp;ar);
-printf("%d\n", ar.linedefined);
-</pre>
-<p>
-Each character in the string <code>what</code>
-selects some fields of the structure <code>ar</code> to be filled or
-a value to be pushed on the stack:
-<ul>
-<li><b>'<code>n</code>': </b> fills in the field <code>name</code> and <code>namewhat</code>;
-</li>
-<li><b>'<code>S</code>': </b>
-fills in the fields <code>source</code>, <code>short_src</code>,
-<code>linedefined</code>, <code>lastlinedefined</code>, and <code>what</code>;
-</li>
-<li><b>'<code>l</code>': </b> fills in the field <code>currentline</code>;
-</li>
-<li><b>'<code>t</code>': </b> fills in the field <code>istailcall</code>;
-</li>
-<li><b>'<code>u</code>': </b> fills in the fields
-<code>nups</code>, <code>nparams</code>, and <code>isvararg</code>;
-</li>
-<li><b>'<code>f</code>': </b>
-pushes onto the stack the function that is
-running at the given level;
-</li>
-<li><b>'<code>L</code>': </b>
-pushes onto the stack a table whose indices are the
-numbers of the lines that are valid on the function.
-(A <em>valid line</em> is a line with some associated code,
-that is, a line where you can put a break point.
-Non-valid lines include empty lines and comments.)
-<p>
-If this option is given together with option '<code>f</code>',
-its table is pushed after the function.
-</li>
-</ul>
-<p>
-This function returns 0 on error
-(for instance, an invalid option in <code>what</code>).
-<hr><h3><a name="lua_getlocal"><code>lua_getlocal</code></a></h3><p>
-<span class="apii">[-0, +(0|1), &ndash;]</span>
-<pre>const char *lua_getlocal (lua_State *L, const 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> must be <code>NULL</code> and the function
-to be inspected must be at the top of the stack.
-In this case, only parameters of Lua functions are visible
-(as there is no information about what variables are active)
-and no values are pushed onto the stack.
-<p>
-Returns <code>NULL</code> (and pushes nothing)
-when the index is greater than
-the number of active local variables.
-<hr><h3><a name="lua_getstack"><code>lua_getstack</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>int lua_getstack (lua_State *L, int level, lua_Debug *ar);</pre>
-<p>
-Gets information about the interpreter runtime stack.
-<p>
-This function fills parts of a <a href="#lua_Debug"><code>lua_Debug</code></a> structure with
-an identification of the <em>activation record</em>
-of the function executing at a given level.
-Level&nbsp;0 is the current running function,
-whereas level <em>n+1</em> is the function that has called level <em>n</em>
-(except for tail calls, which do not count on the stack).
-When there are no errors, <a href="#lua_getstack"><code>lua_getstack</code></a> returns 1;
-when called with a level greater than the stack depth,
-it returns 0.
-<hr><h3><a name="lua_getupvalue"><code>lua_getupvalue</code></a></h3><p>
-<span class="apii">[-0, +(0|1), &ndash;]</span>
-<pre>const char *lua_getupvalue (lua_State *L, int funcindex, int n);</pre>
-<p>
-Gets information about a closure's upvalue.
-(For Lua functions,
-upvalues are the external local variables that the function uses,
-and that are consequently included in its closure.)
-<a href="#lua_getupvalue"><code>lua_getupvalue</code></a> gets the index <code>n</code> of an upvalue,
-pushes the upvalue's value onto the stack,
-and returns its name.
-<code>funcindex</code> points to the closure in the stack.
-(Upvalues have no particular order,
-as they are active through the whole function.
-So, they are numbered in an arbitrary order.)
-<p>
-Returns <code>NULL</code> (and pushes nothing)
-when the index is greater than the number of upvalues.
-For C&nbsp;functions, this function uses the empty string <code>""</code>
-as a name for all upvalues.
-<hr><h3><a name="lua_Hook"><code>lua_Hook</code></a></h3>
-<pre>typedef void (*lua_Hook) (lua_State *L, lua_Debug *ar);</pre>
-<p>
-Type for debugging hook functions.
-<p>
-Whenever a hook is called, its <code>ar</code> argument has its field
-<code>event</code> set to the specific event that triggered the hook.
-Lua identifies these events with the following constants:
-<a name="pdf-LUA_HOOKCALL"><code>LUA_HOOKCALL</code></a>, <a name="pdf-LUA_HOOKRET"><code>LUA_HOOKRET</code></a>,
-<a name="pdf-LUA_HOOKTAILCALL"><code>LUA_HOOKTAILCALL</code></a>, <a name="pdf-LUA_HOOKLINE"><code>LUA_HOOKLINE</code></a>,
-and <a name="pdf-LUA_HOOKCOUNT"><code>LUA_HOOKCOUNT</code></a>.
-Moreover, for line events, the field <code>currentline</code> is also set.
-To get the value of any other field in <code>ar</code>,
-the hook must call <a href="#lua_getinfo"><code>lua_getinfo</code></a>.
-<p>
-For call events, <code>event</code> can be <code>LUA_HOOKCALL</code>,
-the normal value, or <code>LUA_HOOKTAILCALL</code>, for a tail call;
-in this case, there will be no corresponding return event.
-<p>
-While Lua is running a hook, it disables other calls to hooks.
-Therefore, if a hook calls back Lua to execute a function or a chunk,
-this execution occurs without any calls to hooks.
-<p>
-Hook functions cannot have continuations,
-that is, they cannot call <a href="#lua_yieldk"><code>lua_yieldk</code></a>,
-<a href="#lua_pcallk"><code>lua_pcallk</code></a>, or <a href="#lua_callk"><code>lua_callk</code></a> with a non-null <code>k</code>.
-<p>
-Hook functions can yield under the following conditions:
-Only count and line events can yield
-and they cannot yield any value;
-to yield a hook function must finish its execution
-calling <a href="#lua_yield"><code>lua_yield</code></a> with <code>nresults</code> equal to zero.
-<hr><h3><a name="lua_sethook"><code>lua_sethook</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void lua_sethook (lua_State *L, lua_Hook f, int mask, int count);</pre>
-<p>
-Sets the debugging hook function.
-<p>
-Argument <code>f</code> is the hook function.
-<code>mask</code> specifies on which events the hook will be called:
-it is formed by a bitwise or of the constants
-<a name="pdf-LUA_MASKCALL"><code>LUA_MASKCALL</code></a>,
-<a name="pdf-LUA_MASKRET"><code>LUA_MASKRET</code></a>,
-<a name="pdf-LUA_MASKLINE"><code>LUA_MASKLINE</code></a>,
-and <a name="pdf-LUA_MASKCOUNT"><code>LUA_MASKCOUNT</code></a>.
-The <code>count</code> argument is only meaningful when the mask
-includes <code>LUA_MASKCOUNT</code>.
-For each event, the hook is called as explained below:
-<ul>
-<li><b>The call hook: </b> is called when the interpreter calls a function.
-The hook is called just after Lua enters the new function,
-before the function gets its arguments.
-</li>
-<li><b>The return hook: </b> is called when the interpreter returns from a function.
-The hook is called just before Lua leaves the function.
-There is no standard way to access the values
-to be returned by the function.
-</li>
-<li><b>The line hook: </b> is called when the interpreter is about to
-start the execution of a new line of code,
-or when it jumps back in the code (even to the same line).
-(This event only happens while Lua is executing a Lua function.)
-</li>
-<li><b>The count hook: </b> is called after the interpreter executes every
-<code>count</code> instructions.
-(This event only happens while Lua is executing a Lua function.)
-</li>
-</ul>
-<p>
-A hook is disabled by setting <code>mask</code> to zero.
-<hr><h3><a name="lua_setlocal"><code>lua_setlocal</code></a></h3><p>
-<span class="apii">[-(0|1), +0, &ndash;]</span>
-<pre>const char *lua_setlocal (lua_State *L, const lua_Debug *ar, int n);</pre>
-<p>
-Sets the value of a local variable of a given activation record.
-Parameters <code>ar</code> and <code>n</code> are as in <a href="#lua_getlocal"><code>lua_getlocal</code></a>
-(see <a href="#lua_getlocal"><code>lua_getlocal</code></a>).
-<a href="#lua_setlocal"><code>lua_setlocal</code></a> assigns the value at the top of the stack
-to the variable and returns its name.
-It also pops the value from the stack.
-<p>
-Returns <code>NULL</code> (and pops nothing)
-when the index is greater than
-the number of active local variables.
-<hr><h3><a name="lua_setupvalue"><code>lua_setupvalue</code></a></h3><p>
-<span class="apii">[-(0|1), +0, &ndash;]</span>
-<pre>const char *lua_setupvalue (lua_State *L, int funcindex, int n);</pre>
-<p>
-Sets the value of a closure's upvalue.
-It assigns the value at the top of the stack
-to the upvalue and returns its name.
-It also pops the value from the stack.
-Parameters <code>funcindex</code> and <code>n</code> are as in the <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>
-(see <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>).
-<p>
-Returns <code>NULL</code> (and pops nothing)
-when the index is greater than the number of upvalues.
-<hr><h3><a name="lua_upvalueid"><code>lua_upvalueid</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void *lua_upvalueid (lua_State *L, int funcindex, int n);</pre>
-<p>
-Returns a unique identifier for the upvalue numbered <code>n</code>
-from the closure at index <code>funcindex</code>.
-Parameters <code>funcindex</code> and <code>n</code> are as in the <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>
-(see <a href="#lua_getupvalue"><code>lua_getupvalue</code></a>)
-(but <code>n</code> cannot be greater than the number of upvalues).
-<p>
-These unique identifiers allow a program to check whether different
-closures share upvalues.
-Lua closures that share an upvalue
-(that is, that access a same external local variable)
-will return identical ids for those upvalue indices.
-<hr><h3><a name="lua_upvaluejoin"><code>lua_upvaluejoin</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void lua_upvaluejoin (lua_State *L, int funcindex1, int n1,
-int funcindex2, int n2);</pre>
-<p>
-Make the <code>n1</code>-th upvalue of the Lua closure at index <code>funcindex1</code>
-refer to the <code>n2</code>-th upvalue of the Lua closure at index <code>funcindex2</code>.
-<h1>5 &ndash; <a name="5">The Auxiliary Library</a></h1>
-<p>
-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&nbsp;function arguments.
-Because the error message is formatted for arguments
-(e.g., "<code>bad argument #1</code>"),
-you should not use these functions for other stack values.
-<p>
-Functions called <code>luaL_check*</code>
-always raise an error if the check is not satisfied.
-<h2>5.1 &ndash; <a name="5.1">Functions and Types</a></h2>
-<p>
-Here we list all functions and types from the auxiliary library
-in alphabetical order.
-<hr><h3><a name="luaL_addchar"><code>luaL_addchar</code></a></h3><p>
-<span class="apii">[-?, +?, <em>e</em>]</span>
-<pre>void luaL_addchar (luaL_Buffer *B, char c);</pre>
-<p>
-Adds the byte <code>c</code> to the buffer <code>B</code>
-(see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
-<hr><h3><a name="luaL_addlstring"><code>luaL_addlstring</code></a></h3><p>
-<span class="apii">[-?, +?, <em>e</em>]</span>
-<pre>void luaL_addlstring (luaL_Buffer *B, const char *s, size_t l);</pre>
-<p>
-Adds the string pointed to by <code>s</code> with length <code>l</code> to
-the buffer <code>B</code>
-(see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
-The string can contain embedded zeros.
-<hr><h3><a name="luaL_addsize"><code>luaL_addsize</code></a></h3><p>
-<span class="apii">[-?, +?, <em>e</em>]</span>
-<pre>void luaL_addsize (luaL_Buffer *B, size_t n);</pre>
-<p>
-Adds to the buffer <code>B</code> (see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>)
-a string of length <code>n</code> previously copied to the
-buffer area (see <a href="#luaL_prepbuffer"><code>luaL_prepbuffer</code></a>).
-<hr><h3><a name="luaL_addstring"><code>luaL_addstring</code></a></h3><p>
-<span class="apii">[-?, +?, <em>e</em>]</span>
-<pre>void luaL_addstring (luaL_Buffer *B, const char *s);</pre>
-<p>
-Adds the zero-terminated string pointed to by <code>s</code>
-to the buffer <code>B</code>
-(see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
-<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 it is not, raises an error with a standard message (see <a href="#luaL_argerror"><code>luaL_argerror</code></a>).
-<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 reporting a problem with argument <code>arg</code>
-of the C function that called it,
-using a standard message
-that includes <code>extramsg</code> as a comment:
-<pre>
-bad argument #<em>arg</em> to '<em>funcname</em>' (<em>extramsg</em>)
-</pre><p>
-This function never returns.
-<hr><h3><a name="luaL_Buffer"><code>luaL_Buffer</code></a></h3>
-<pre>typedef struct luaL_Buffer luaL_Buffer;</pre>
-<p>
-Type for a <em>string buffer</em>.
-<p>
-A string buffer allows C&nbsp;code to build Lua strings piecemeal.
-Its pattern of use is as follows:
-<ul>
-<li>First declare a variable <code>b</code> of type <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>.</li>
-<li>Then initialize it with a call <code>luaL_buffinit(L, &amp;b)</code>.</li>
-<li>
-Then add string pieces to the buffer calling any of
-the <code>luaL_add*</code> functions.
-</li>
-<li>
-Finish by calling <code>luaL_pushresult(&amp;b)</code>.
-This call leaves the final string on the top of the stack.
-</li>
-</ul>
-<p>
-If you know beforehand the total size of the resulting string,
-you can use the buffer like this:
-<ul>
-<li>First declare a variable <code>b</code> of type <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>.</li>
-<li>Then initialize it and preallocate a space of
-size <code>sz</code> with a call <code>luaL_buffinitsize(L, &amp;b, sz)</code>.</li>
-<li>Then copy the string into that space.</li>
-<li>
-Finish by calling <code>luaL_pushresultsize(&amp;b, sz)</code>,
-where <code>sz</code> is the total size of the resulting string
-copied into that space.
-</li>
-</ul>
-<p>
-During its normal operation,
-a string buffer uses a variable number of stack slots.
-So, while using a buffer, you cannot assume that you know where
-the top of the stack is.
-You can use the stack between successive calls to buffer operations
-as long as that use is balanced;
-that is,
-when you call a buffer operation,
-the stack is at the same level
-it was immediately after the previous buffer operation.
-(The only exception to this rule is <a href="#luaL_addvalue"><code>luaL_addvalue</code></a>.)
-After calling <a href="#luaL_pushresult"><code>luaL_pushresult</code></a> the stack is back to its
-level when the buffer was initialized,
-plus the final string on its top.
-<hr><h3><a name="luaL_buffinit"><code>luaL_buffinit</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void luaL_buffinit (lua_State *L, luaL_Buffer *B);</pre>
-<p>
-Initializes a buffer <code>B</code>.
-This function does not allocate any space;
-the buffer must be declared as a variable
-(see <a href="#luaL_Buffer"><code>luaL_Buffer</code></a>).
-<hr><h3><a name="luaL_buffinitsize"><code>luaL_buffinitsize</code></a></h3><p>
-<span class="apii">[-?, +?, <em>e</em>]</span>
-<pre>char *luaL_buffinitsize (lua_State *L, luaL_Buffer *B, size_t sz);</pre>
-<p>
-Equivalent to the sequence
-<a href="#luaL_buffinit"><code>luaL_buffinit</code></a>, <a href="#luaL_prepbuffsize"><code>luaL_prepbuffsize</code></a>.
-<hr><h3><a name="luaL_callmeta"><code>luaL_callmeta</code></a></h3><p>
-<span class="apii">[-0, +(0|1), <em>e</em>]</span>
-<pre>int luaL_callmeta (lua_State *L, int obj, const char *e);</pre>
-<p>
-Calls a metamethod.
-<p>
-If the object at index <code>obj</code> has a metatable and this
-metatable has a field <code>e</code>,
-this function calls this field passing the object as its only argument.
-In this case this function returns true and pushes onto the
-stack the value returned by the call.
-If there is no metatable or no metamethod,
-this function returns false (without pushing any value on the stack).
-<hr><h3><a name="luaL_checkany"><code>luaL_checkany</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>void luaL_checkany (lua_State *L, int arg);</pre>
-<p>
-Checks whether the function has an argument
-of any type (including <b>nil</b>) at position <code>arg</code>.
-<hr><h3><a name="luaL_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 an integer
-(or can be converted to an integer)
-and returns this integer cast to a <a href="#lua_Integer"><code>lua_Integer</code></a>.
-<hr><h3><a name="luaL_checklstring"><code>luaL_checklstring</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>const char *luaL_checklstring (lua_State *L, int arg, size_t *l);</pre>
-<p>
-Checks whether the function argument <code>arg</code> is a string
-and returns this string;
-if <code>l</code> is not <code>NULL</code> fills <code>*l</code>
-with the string's length.
-<p>
-This function uses <a href="#lua_tolstring"><code>lua_tolstring</code></a> to get its result,
-so all conversions and caveats of that function apply here.
-<hr><h3><a name="luaL_checknumber"><code>luaL_checknumber</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>lua_Number luaL_checknumber (lua_State *L, int arg);</pre>
-<p>
-Checks whether the function argument <code>arg</code> is a number
-and returns this number.
-<hr><h3><a name="luaL_checkoption"><code>luaL_checkoption</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>int luaL_checkoption (lua_State *L,
-int arg,
-const char *def,
-const char *const lst[]);</pre>
-<p>
-Checks whether the function argument <code>arg</code> is a string and
-searches for this string in the array <code>lst</code>
-(which must be NULL-terminated).
-Returns the index in the array where the string was found.
-Raises an error if the argument is not a string or
-if the string cannot be found.
-<p>
-If <code>def</code> is not <code>NULL</code>,
-the function uses <code>def</code> as a default value when
-there is no argument <code>arg</code> or when this argument is <b>nil</b>.
-<p>
-This is a useful function for mapping strings to C&nbsp;enums.
-(The usual convention in Lua libraries is
-to use strings instead of numbers to select options.)
-<hr><h3><a name="luaL_checkstack"><code>luaL_checkstack</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>void luaL_checkstack (lua_State *L, int sz, const char *msg);</pre>
-<p>
-Grows the stack size to <code>top + sz</code> elements,
-raising an error if the stack cannot grow to that size.
-<code>msg</code> is an additional text to go into the error message
-(or <code>NULL</code> for no additional text).
-<hr><h3><a name="luaL_checkstring"><code>luaL_checkstring</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>const char *luaL_checkstring (lua_State *L, int arg);</pre>
-<p>
-Checks whether the function argument <code>arg</code> is a string
-and returns this string.
-<p>
-This function uses <a href="#lua_tolstring"><code>lua_tolstring</code></a> to get its result,
-so all conversions and caveats of that function apply here.
-<hr><h3><a name="luaL_checktype"><code>luaL_checktype</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>void luaL_checktype (lua_State *L, int arg, int t);</pre>
-<p>
-Checks whether the function argument <code>arg</code> has type <code>t</code>.
-See <a href="#lua_type"><code>lua_type</code></a> for the encoding of types for <code>t</code>.
-<hr><h3><a name="luaL_checkudata"><code>luaL_checkudata</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>void *luaL_checkudata (lua_State *L, int arg, const char *tname);</pre>
-<p>
-Checks whether the function argument <code>arg</code> is a userdata
-of the type <code>tname</code> (see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code></a>) and
-returns the userdata address (see <a href="#lua_touserdata"><code>lua_touserdata</code></a>).
-<hr><h3><a name="luaL_checkversion"><code>luaL_checkversion</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void luaL_checkversion (lua_State *L);</pre>
-<p>
-Checks whether the core running the call,
-the core that created the Lua state,
-and the code making the call are all using the same version of Lua.
-Also checks whether the core running the call
-and the core that created the Lua state
-are using the same address space.
-<hr><h3><a name="luaL_dofile"><code>luaL_dofile</code></a></h3><p>
-<span class="apii">[-0, +?, <em>e</em>]</span>
-<pre>int luaL_dofile (lua_State *L, const char *filename);</pre>
-<p>
-Loads and runs the given file.
-It is defined as the following macro:
-<pre>
-(luaL_loadfile(L, filename) || lua_pcall(L, 0, LUA_MULTRET, 0))
-</pre><p>
-It returns false if there are no errors
-or true in case of errors.
-<hr><h3><a name="luaL_dostring"><code>luaL_dostring</code></a></h3><p>
-<span class="apii">[-0, +?, &ndash;]</span>
-<pre>int luaL_dostring (lua_State *L, const char *str);</pre>
-<p>
-Loads and runs the given string.
-It is defined as the following macro:
-<pre>
-(luaL_loadstring(L, str) || lua_pcall(L, 0, LUA_MULTRET, 0))
-</pre><p>
-It returns false if there are no errors
-or true in case of errors.
-<hr><h3><a name="luaL_error"><code>luaL_error</code></a></h3><p>
-<span class="apii">[-0, +0, <em>v</em>]</span>
-<pre>int luaL_error (lua_State *L, const char *fmt, ...);</pre>
-<p>
-Raises an error.
-The error message format is given by <code>fmt</code>
-plus any extra arguments,
-following the same rules of <a href="#lua_pushfstring"><code>lua_pushfstring</code></a>.
-It also adds at the beginning of the message the file name and
-the line number where the error occurred,
-if this information is available.
-<p>
-This function never returns,
-but it is an idiom to use it in C&nbsp;functions
-as <code>return luaL_error(<em>args</em>)</code>.
-<hr><h3><a name="luaL_execresult"><code>luaL_execresult</code></a></h3><p>
-<span class="apii">[-0, +3, <em>e</em>]</span>
-<pre>int luaL_execresult (lua_State *L, int stat);</pre>
-<p>
-This function produces the return values for
-process-related functions in the standard library
-(<a href="#pdf-os.execute"><code>os.execute</code></a> and <a href="#pdf-io.close"><code>io.close</code></a>).
-<hr><h3><a name="luaL_fileresult"><code>luaL_fileresult</code></a></h3><p>
-<span class="apii">[-0, +(1|3), <em>e</em>]</span>
-<pre>int luaL_fileresult (lua_State *L, int stat, const char *fname);</pre>
-<p>
-This function produces the return values for
-file-related functions in the standard library
-(<a href="#pdf-io.open"><code>io.open</code></a>, <a href="#pdf-os.rename"><code>os.rename</code></a>, <a href="#pdf-file:seek"><code>file:seek</code></a>, etc.).
-<hr><h3><a name="luaL_getmetafield"><code>luaL_getmetafield</code></a></h3><p>
-<span class="apii">[-0, +(0|1), <em>e</em>]</span>
-<pre>int luaL_getmetafield (lua_State *L, int obj, const char *e);</pre>
-<p>
-Pushes onto the stack the field <code>e</code> from the metatable
-of the object at index <code>obj</code> and returns the type of pushed value.
-If the object does not have a metatable,
-or if the metatable does not have this field,
-pushes nothing and returns <code>LUA_TNIL</code>.
-<hr><h3><a name="luaL_getmetatable"><code>luaL_getmetatable</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>int 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>).
-If there is no metatable associated with <code>tname</code>,
-returns false and pushes <b>nil</b>.
-<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>lua_Integer 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="#3.4.7">&sect;3.4.7</a>).
-Raises an error if the result of the operation is not an integer.
-(This case only can happen through metamethods.)
-<hr><h3><a name="luaL_loadbuffer"><code>luaL_loadbuffer</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>int luaL_loadbuffer (lua_State *L,
-const char *buff,
-size_t sz,
-const char *name);</pre>
-<p>
-Equivalent to <a href="#luaL_loadbufferx"><code>luaL_loadbufferx</code></a> with <code>mode</code> equal to <code>NULL</code>.
-<hr><h3><a name="luaL_loadbufferx"><code>luaL_loadbufferx</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>int luaL_loadbufferx (lua_State *L,
-const char *buff,
-size_t sz,
-const char *name,
-const char *mode);</pre>
-<p>
-Loads a buffer as a Lua chunk.
-This function uses <a href="#lua_load"><code>lua_load</code></a> to load the chunk in the
-buffer pointed to by <code>buff</code> with size <code>sz</code>.
-<p>
-This function returns the same results as <a href="#lua_load"><code>lua_load</code></a>.
-<code>name</code> is the chunk name,
-used for debug information and error messages.
-The string <code>mode</code> works as in function <a href="#lua_load"><code>lua_load</code></a>.
-<hr><h3><a name="luaL_loadfile"><code>luaL_loadfile</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>int luaL_loadfile (lua_State *L, const char *filename);</pre>
-<p>
-Equivalent to <a href="#luaL_loadfilex"><code>luaL_loadfilex</code></a> with <code>mode</code> equal to <code>NULL</code>.
-<hr><h3><a name="luaL_loadfilex"><code>luaL_loadfilex</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>int luaL_loadfilex (lua_State *L, const char *filename,
-const char *mode);</pre>
-<p>
-Loads a file as a Lua chunk.
-This function uses <a href="#lua_load"><code>lua_load</code></a> to load the chunk in the file
-named <code>filename</code>.
-If <code>filename</code> is <code>NULL</code>,
-then it loads from the standard input.
-The first line in the file is ignored if it starts with a <code>#</code>.
-<p>
-The string <code>mode</code> works as in function <a href="#lua_load"><code>lua_load</code></a>.
-<p>
-This function returns the same results as <a href="#lua_load"><code>lua_load</code></a>,
-but it has an extra error code <a name="pdf-LUA_ERRFILE"><code>LUA_ERRFILE</code></a>
-if it cannot open/read the file or the file has a wrong mode.
-<p>
-As <a href="#lua_load"><code>lua_load</code></a>, this function only loads the chunk;
-it does not run it.
-<hr><h3><a name="luaL_loadstring"><code>luaL_loadstring</code></a></h3><p>
-<span class="apii">[-0, +1, &ndash;]</span>
-<pre>int luaL_loadstring (lua_State *L, const char *s);</pre>
-<p>
-Loads a string as a Lua chunk.
-This function uses <a href="#lua_load"><code>lua_load</code></a> to load the chunk in
-the zero-terminated string <code>s</code>.
-<p>
-This function returns the same results as <a href="#lua_load"><code>lua_load</code></a>.
-<p>
-Also as <a href="#lua_load"><code>lua_load</code></a>, this function only loads the chunk;
-it does not run it.
-<hr><h3><a name="luaL_newlib"><code>luaL_newlib</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void luaL_newlib (lua_State *L, const luaL_Reg l[]);</pre>
-<p>
-Creates a new table and registers there
-the functions in list <code>l</code>.
-<p>
-It is implemented as the following macro:
-<pre>
-(luaL_newlibtable(L,l), luaL_setfuncs(L,l,0))
-</pre><p>
-The array <code>l</code> must be the actual array,
-not a pointer to it.
-<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 to this new table the pair <code>__name = tname</code>,
-adds to the registry the pair <code>[tname] = new table</code>,
-and returns 1.
-(The entry <code>__name</code> is used by some error-reporting functions.)
-<p>
-In both cases pushes onto the stack the final value associated
-with <code>tname</code> in the registry.
-<hr><h3><a name="luaL_newstate"><code>luaL_newstate</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>lua_State *luaL_newstate (void);</pre>
-<p>
-Creates a new Lua state.
-It calls <a href="#lua_newstate"><code>lua_newstate</code></a> with an
-allocator based on the standard&nbsp;C <code>realloc</code> function
-and then sets a panic function (see <a href="#4.6">&sect;4.6</a>) that prints
-an error message to the standard error output in case of fatal
-errors.
-<p>
-Returns the new state,
-or <code>NULL</code> if there is a memory allocation error.
-<hr><h3><a name="luaL_openlibs"><code>luaL_openlibs</code></a></h3><p>
-<span class="apii">[-0, +0, <em>e</em>]</span>
-<pre>void luaL_openlibs (lua_State *L);</pre>
-<p>
-Opens all standard Lua libraries into the given state.
-<hr><h3><a name="luaL_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 an integer
-(or convertible to an integer),
-returns this integer.
-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_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 a 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>
-If <code>modname</code> is not already present in <a href="#pdf-package.loaded"><code>package.loaded</code></a>,
-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 module into global <code>modname</code>.
-<p>
-Leaves a copy of the module on the stack.
-<hr><h3><a name="luaL_setfuncs"><code>luaL_setfuncs</code></a></h3><p>
-<span class="apii">[-nup, +0, <em>e</em>]</span>
-<pre>void luaL_setfuncs (lua_State *L, const luaL_Reg *l, int nup);</pre>
-<p>
-Registers all functions in the array <code>l</code>
-(see <a href="#luaL_Reg"><code>luaL_Reg</code></a>) into the table on the top of the stack
-(below optional upvalues, see next).
-<p>
-When <code>nup</code> is not zero,
-all functions are created sharing <code>nup</code> upvalues,
-which must be previously pushed on the stack
-on top of the library table.
-These values are popped from the stack after the registration.
-<hr><h3><a name="luaL_setmetatable"><code>luaL_setmetatable</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void luaL_setmetatable (lua_State *L, const char *tname);</pre>
-<p>
-Sets the metatable of the object at the top of the stack
-as the metatable associated with name <code>tname</code>
-in the registry (see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code></a>).
-<hr><h3><a name="luaL_Stream"><code>luaL_Stream</code></a></h3>
-<pre>typedef struct luaL_Stream {
-FILE *f;
-lua_CFunction closef;
-} luaL_Stream;</pre>
-<p>
-The standard representation for file handles,
-which is used by the standard I/O library.
-<p>
-A file handle is implemented as a full userdata,
-with a metatable called <code>LUA_FILEHANDLE</code>
-(where <code>LUA_FILEHANDLE</code> is a macro with the actual metatable's name).
-The metatable is created by the I/O library
-(see <a href="#luaL_newmetatable"><code>luaL_newmetatable</code></a>).
-<p>
-This userdata must start with the structure <code>luaL_Stream</code>;
-it can contain other data after this initial structure.
-Field <code>f</code> points to the corresponding C stream
-(or it can be <code>NULL</code> to indicate an incompletely created handle).
-Field <code>closef</code> points to a Lua function
-that will be called to close the stream
-when the handle is closed or collected;
-this function receives the file handle as its sole argument and
-must return either <b>true</b> (in case of success)
-or <b>nil</b> plus an error message (in case of error).
-Once Lua calls this field,
-the field value is changed to <code>NULL</code>
-to signal that the handle is closed.
-<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 raising an error.
-<hr><h3><a name="luaL_tolstring"><code>luaL_tolstring</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>const char *luaL_tolstring (lua_State *L, int idx, size_t *len);</pre>
-<p>
-Converts any Lua value at the given index to a C&nbsp;string
-in a reasonable format.
-The resulting string is pushed onto the stack and also
-returned by the function.
-If <code>len</code> is not <code>NULL</code>,
-the function also sets <code>*len</code> with the string length.
-<p>
-If the value has a metatable with a <code>"__tostring"</code> field,
-then <code>luaL_tolstring</code> calls the corresponding metamethod
-with the value as argument,
-and uses the result of the call as its result.
-<hr><h3><a name="luaL_traceback"><code>luaL_traceback</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void luaL_traceback (lua_State *L, lua_State *L1, const char *msg,
-int level);</pre>
-<p>
-Creates and pushes a traceback of the stack <code>L1</code>.
-If <code>msg</code> is not <code>NULL</code> it is appended
-at the beginning of the traceback.
-The <code>level</code> parameter tells at which level
-to start the traceback.
-<hr><h3><a name="luaL_typename"><code>luaL_typename</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>const char *luaL_typename (lua_State *L, int index);</pre>
-<p>
-Returns the name of the type of the value at the given index.
-<hr><h3><a name="luaL_unref"><code>luaL_unref</code></a></h3><p>
-<span class="apii">[-0, +0, &ndash;]</span>
-<pre>void luaL_unref (lua_State *L, int t, int ref);</pre>
-<p>
-Releases reference <code>ref</code> from the table at index <code>t</code>
-(see <a href="#luaL_ref"><code>luaL_ref</code></a>).
-The entry is removed from the table,
-so that the referred object can be collected.
-The reference <code>ref</code> is also freed to be used again.
-<p>
-If <code>ref</code> is <a href="#pdf-LUA_NOREF"><code>LUA_NOREF</code></a> or <a href="#pdf-LUA_REFNIL"><code>LUA_REFNIL</code></a>,
-<a href="#luaL_unref"><code>luaL_unref</code></a> does nothing.
-<hr><h3><a name="luaL_where"><code>luaL_where</code></a></h3><p>
-<span class="apii">[-0, +1, <em>e</em>]</span>
-<pre>void luaL_where (lua_State *L, int lvl);</pre>
-<p>
-Pushes onto the stack a string identifying the current position
-of the control at level <code>lvl</code> in the call stack.
-Typically this string has the following format:
-<pre>
-<em>chunkname</em>:<em>currentline</em>:
-</pre><p>
-Level&nbsp;0 is the running function,
-level&nbsp;1 is the function that called the running function,
-etc.
-<p>
-This function is used to build a prefix for error messages.

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