Runs operations on a new Lua State. The state is created when the function is called and closed on return. The state, and all pointers to values within it, must not be used after the function returns.

Example

Run a small Lua operation (prints the major version of Lua).

withNewState $ \l -> do
  luaL_openlibs l
  withCString "print" (lua_getglobal l)
  withCString "_VERSION" (lua_getglobal l)
  lua_pcall l (NumArgs 1) (NumResults 1) (StackIndex 0)

Since: 2.0.0

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.

Synonym for lua_State *. See lua_State.

The reader function used by load. Every time it needs another piece of the chunk, lua_load calls the reader, passing along its data parameter. The reader must return a pointer to a block of memory with a new piece of the chunk and set size 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 NULL or set size to zero. The reader function may return pieces of any size greater than zero.

See lua_Reader.

Type for C functions.

In order to communicate properly with Lua, a C function must use the following protocol, which defines the way parameters and results are passed: a C function receives its arguments from Lua in its stack in direct order (the first argument is pushed first). So, when the function starts, lua_gettop 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 lua_gettop. To return values to Lua, a C function just pushes them onto the stack, in direct order (the first result is pushed first), and returns the number of results. Any other value in the stack below the results will be properly discarded by Lua. Like a Lua function, a C function called by Lua can also return many results.

See lua_CFunction.

Type of Haskell functions that can be turned into C functions.

This is the same as a dereferenced CFunction.

The type of integers in Lua.

By default this type is Int64, but that can be changed to different values in Lua. (See LUA_INT_TYPE in luaconf.h.)

See lua_Integer.

The type of floats in Lua.

By default this type is Double, but that can be changed in Lua to a single float or a long double. (See LUA_FLOAT_TYPE in luaconf.h.)

See lua_Number.

Boolean value returned by a Lua C API function. This is a CInt and should be interpreted as False iff the value is 0, True otherwise.

Value which Lua usually uses as True.

Value which Lua usually uses as False.

A stack index

Stack index of the Lua registry.

The number of arguments consumed curing a function call.

The number of results returned by a function call.

Option for multiple returns in lua_pcall.

Integer code used to encode the type of a Lua value.

Non-valid stack index

Type of Lua's nil value

Type of Lua booleans

Type of light userdata

Type of Lua numbers. See Number

Type of Lua string values

Type of Lua tables

Type of functions, either normal or CFunction

Type of full user data

Type of Lua threads

Relational operator code.

Compares for equality (==)

Compares for less than (<)

Compares for less or equal (<=)

Performs addition (+).

Performs subtraction (-)

Performs multiplication (*)

Performs float division (/)

Performs floor division (//)

Performs modulo (%)

Performs exponentiation (^)

Performs mathematical negation (unary -)

Performs bitwise NOT (~)

Performs bitwise AND (&)

Performs bitwise OR (|)

Performs bitwise exclusive OR (~)

Performs left shift (<<)

Performs right shift (>>)

Integer code used to signal the status of a thread or computation.

Success.

Yielding / suspended coroutine.

A runtime error.

A syntax error.

Memory allocation error. For such errors, Lua does not call the message handler.

Error while running a __gc metamethod. For such errors, Lua does not call the message handler (as this kind of error typically has no relation with the function being called).

Error while running the message handler.

File related error (e.g., the file cannot be opened or read).

Stack index of the nth element from the top of the stack.

Since: 2.0.0

Stack index of the nth element from the bottom of the stack.

Since: 2.0.0

Alias for nthTop.

Since: 2.0.0

Index of the topmost stack element.

Since: 2.0.0

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. In 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.

https://www.lua.org/manual/5.3/manual.html#lua_close

Creates a new thread, pushes it on the stack, and returns a State 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.

There is no explicit function to close or to destroy a thread. Threads are subject to garbage collection, like any Lua object.

https://www.lua.org/manual/5.3/manual.html#lua_newthread

Returns the address of the version number (a C static variable) stored in the Lua core. When called with a valid State, returns the address of the version used to create that state. When called with NULL, returns the address of the version running the call.

https://www.lua.org/manual/5.3/manual.html#lua_version

Converts the acceptable index idx into an equivalent absolute index (that is, one that does not depend on the stack top).

https://www.lua.org/manual/5.3/manual.html#lua_absindex

Returns the index of the top element in the stack. Because indices start at 1, this result is equal to the number of elements in the stack (and so 0 means an empty stack).

https://www.lua.org/manual/5.3/manual.html#lua_gettop

Accepts any index, or 0, and sets the stack top to this index. If the new top is larger than the old one, then the new elements are filled with *nil*. If index is 0, then all stack elements are removed.

https://www.lua.org/manual/5.3/manual.html#lua_settop

Pushes a copy of the element at the given index onto the stack.

https://www.lua.org/manual/5.3/manual.html#lua_pushvalue

Pops n elements from the stack.

https://www.lua.org/manual/5.3/manual.html#lua_pop

Copies the element at index fromidx into the valid index toidx, replacing the value at that position. Values at other positions are not affected.

https://www.lua.org/manual/5.3/manual.html#lua_copy

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.

https://www.lua.org/manual/5.3/manual.html#lua_remove

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.

https://www.lua.org/manual/5.3/manual.html#lua_insert

Moves the top element into the given valid index without shifting any element (therefore replacing the value at that given index), and then pops the top element.

https://www.lua.org/manual/5.3/manual.html#lua_replace

Rotates the stack elements between the valid index idx and the top of the stack. The elements are rotated n positions in the direction of the top, for a positive n, or -n positions in the direction of the bottom, for a negative n. The absolute value of n must not be greater than the size of the slice being rotated. This function cannot be called with a pseudo-index, because a pseudo-index is not an actual stack position.

https://www.lua.org/manual/5.3/manual.html#lua_rotate

Ensures that the stack has space for at least n extra slots (that is, that you can safely push up to n values into it). 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 already has space for the extra slots, it is left unchanged.

https://www.lua.org/manual/5.3/manual.html#lua_checkstack

Returns TRUE if the value at the given index is nil, and FALSE otherwise.

https://www.lua.org/manual/5.3/manual.html#lua_isnil

Returns TRUE if the value at the given index is a boolean, and FALSE otherwise.

https://www.lua.org/manual/5.3/manual.html#lua_isboolean

Returns TRUE if the value at the given index is a number or a string convertible to a number, and FALSE otherwise.

https://www.lua.org/manual/5.3/manual.html#lua_isnumber

Returns TRUE if the value at the given index is an integer (that is, the value is a number and is represented as an integer), and FALSE otherwise.

https://www.lua.org/manual/5.3/manual.html#lua_isinteger

Returns TRUE if the value at the given index is a string or a number (which is always convertible to a string), and FALSE otherwise.

https://www.lua.org/manual/5.3/manual.html#lua_isstring

Returns TRUE if the value at the given index is a function (either C or Lua), and FALSE otherwise.

https://www.lua.org/manual/5.3/manual.html#lua_isfunction

Returns TRUE if the value at the given index is a table, and FALSE otherwise.

https://www.lua.org/manual/5.3/manual.html#lua_istable

Returns TRUE if the value at the given index is a C function, and FALSE otherwise.

https://www.lua.org/manual/5.3/manual.html#lua_iscfunction

Returns TRUE if the value at the given index is a userdata (either full or light), and FALSE otherwise.

https://www.lua.org/manual/5.3/manual.html#lua_isuserdata

Returns TRUE if the value at the given index is a light userdata, and FALSE otherwise.

https://www.lua.org/manual/5.3/manual.html#lua_islightuserdata

Returns TRUE if the value at the given index is a thread, and FALSE otherwise.

https://www.lua.org/manual/5.3/manual.html#lua_isthread

Returns TRUE if the given index is not valid, and FALSE otherwise.

https://www.lua.org/manual/5.3/manual.html#lua_isnone

Returns TRUE if the given index is not valid or if the value at the given index is nil, and FALSE otherwise.

https://www.lua.org/manual/5.3/manual.html#lua_isnoneornil

Returns the type of the value in the given valid index, or LUA_TNONE for a non-valid (but acceptable) index.

https://www.lua.org/manual/5.3/manual.html#lua_type

Returns the name of the type encoded by the value tp, which must be one the values returned by lua_type.

https://www.lua.org/manual/5.3/manual.html#lua_typename

Returns True if the two values in indices idx1 and idx2 are primitively equal (that is, without calling the __eq metamethod). Otherwise returns False. Also returns False if any of the indices are not valid.

https://www.lua.org/manual/5.3/manual.html#lua_rawequal

Converts the Lua value at the given index to a haskell boolean value. Like all tests in Lua, toboolean returns True for any Lua value different from *false* and *nil*; otherwise it returns False. (If you want to accept only actual boolean values, use lua_isboolean to test the value's type.)

https://www.lua.org/manual/5.3/manual.html#lua_toboolean

Converts a value at the given index to a C function. That value must be a C function; otherwise, returns Nothing.

https://www.lua.org/manual/5.3/manual.html#lua_tocfunction

Converts the Lua value at the given acceptable index to the signed integral type Integer. The Lua value must be an integer, a number, or a string convertible to an integer (see §3.4.3 of the Lua 5.3 Reference Manual); otherwise, lua_tointegerx returns 0.

If the number is not an integer, it is truncated in some non-specified way.

If isnum is not NULL, its referent is assigned a boolean value that indicates whether the operation succeeded.

https://www.lua.org/manual/5.3/manual.html#lua_tointegerx

Converts the Lua value at the given index to the C type lua_Number (see lua_Number). The Lua value must be a number or a string convertible to a number (see §3.4.3); otherwise, lua_tonumberx returns 0.

If isnum is not NULL, its referent is assigned a boolean value that indicates whether the operation succeeded.

https://www.lua.org/manual/5.3/manual.html#lua_tonumberx

Converts the Lua value at the given index to a C string. If len is not NULL, it sets the referent with the string length. The Lua value must be a string or a number; otherwise, the function returns NULL. If the value is a number, then lua_tolstring also changes the actual value in the stack to a string. (This change confuses lua_next when lua_tolstring is applied to keys during a table traversal.)

lua_tolstring returns a pointer to a string inside the Lua state. This string always has a zero ('0') after its last character (as in C), but can contain other zeros in its body.

Because Lua has garbage collection, there is no guarantee that the pointer returned by lua_tolstring will be valid after the corresponding Lua value is removed from the stack.

https://www.lua.org/manual/5.3/manual.html#lua_tolstring

Converts the value at the given index to a generic C pointer (void*). The value can be a userdata, a table, a thread, or a function; otherwise, lua_topointer returns nullPtr. Different objects will give different pointers. There is no way to convert the pointer back to its original value.

Typically this function is used only for hashing and debug information.

https://www.lua.org/manual/5.3/manual.html#lua_topointer

Converts the value at the given index to a Lua thread (represented as State). This value must be a thread; otherwise, the function returns nullPtr.

https://www.lua.org/manual/5.3/manual.html#lua_tothread

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 nullPtr.

https://www.lua.org/manual/5.3/manual.html#lua_touserdata

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 (#) with no metamethods; for userdata, this is the size of the block of memory allocated for the userdata; for other values, it is 0.

https://www.lua.org/manual/5.3/manual.html#lua_rawlen.

Pushes a nil value onto the stack.

https://www.lua.org/manual/5.3/manual.html#lua_pushnil.

Pushes a float with the given value onto the stack.

https://www.lua.org/manual/5.3/manual.html#lua_pushnumber.

Pushes an integer with with the given value onto the stack.

https://www.lua.org/manual/5.3/manual.html#lua_pushinteger.

Pushes the string pointed to by s with size len onto the stack. Lua makes (or reuses) an internal copy of the given string, so the memory at s can be freed or reused immediately after the function returns. The string can contain any binary data, including embedded zeros.

Returns a pointer to the internal copy of the string.

https://www.lua.org/manual/5.3/manual.html#lua_pushlstring.

Pushes the zero-terminated string pointed to by s onto the stack. Lua makes (or reuses) an internal copy of the given string, so the memory at s can be freed or reused immediately after the function returns.

Returns a pointer to the internal copy of the string.

If s is NULL, pushes nil and returns NULL.

Pushes a new C closure onto the stack.

When a C function is created, it is possible to associate some values with it, thus creating a C closure (see §3.4); these values are then accessible to the function whenever it is called. To associate values with a C function, first these values should be pushed onto the stack (when there are multiple values, the first value is pushed first). Then lua_pushcclosure is called to create and push the C function onto the stack, with the argument n telling how many values should be associated with the function. lua_pushcclosure also pops these values from the stack.

The maximum value for n is 255.

https://www.lua.org/manual/5.3/manual.html#lua_pushcclosure.

Pushes a C function onto the stack. This function receives a pointer to a C function and pushes onto the stack a Lua value of type function that, when called, invokes the corresponding C function.

Any function to be callable by Lua must follow the correct protocol to receive its parameters and return its results (see CFunction).

https://www.lua.org/manual/5.3/manual.html#lua_pushcfunction.

Pushes a boolean value with the given value onto the stack.

https://www.lua.org/manual/5.3/manual.html#lua_pushboolean.

Pushes a light userdata onto the stack.

Userdata represent C values in Lua. A light userdata represents a pointer, a Ptr () (i.e., void* in C lingo). It is a value (like a number): you do not create it, it has no individual metatable, and it is not collected (as it was never created). A light userdata is equal to "any" light userdata with the same C address.

https://www.lua.org/manual/5.3/manual.html#lua_pushlightuserdata.

Pushes the current thread onto the stack. Returns 1 iff this thread is the main thread of its state.

https://www.lua.org/manual/5.3/manual.html#lua_pushthread.

Similar to lua_gettable, but does a raw access (i.e., without metamethods).

https://www.lua.org/manual/5.3/manual.html#lua_rawget.

Pushes onto the stack the value t[n], where t is the table at the given index. The access is raw, that is, it does not invoke the __index metamethod.

https://www.lua.org/manual/5.3/manual.html#lua_rawgeti.

Creates a new empty table and pushes it onto the stack. Parameter narr is a hint for how many elements the table will have as a sequence; parameter nrec 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 preallocation is useful for performance when you know in advance how many elements the table will have. Otherwise you can use the function lua_newtable.

https://www.lua.org/manual/5.3/manual.html#lua_createtable.

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.

https://www.lua.org/manual/5.3/manual.html#lua_newuserdata.

If the value at the given index has a metatable, the function pushes that metatable onto the stack and returns 1. Otherwise, the function returns 0 and pushes nothing on the stack.

https://www.lua.org/manual/5.3/manual.html#lua_getmetatable.

Pushes onto the stack the Lua value associated with the full userdata at the given index.

Returns the type of the pushed value.

https://www.lua.org/manual/5.3/manual.html#lua_getuservalue

Pushes onto the stack the value of the global name. Returns the type of that value.

WARNING: lua_getglobal is unsafe in Haskell: if the call to a metamethod triggers an error, then that error cannot be handled and will lead to an unrecoverable program crash. Consider using the hslua_getglobal ersatz function instead. Likewise, the metamethod may not call a Haskell function unless the library was compiled without allow-unsafe-gc.

https://www.lua.org/manual/5.3/manual.html#lua_getglobal.

Pushes onto the stack the value t[k], where t is the value at the given index and k is the value at the top of the stack.

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 §2.4).

Returns the type of the pushed value.

WARNING: lua_gettable is unsafe in Haskell: if the call to a metamethod triggers an error, then that error cannot be handled and will lead to an unrecoverable program crash. Consider using the hslua_gettable ersatz function instead. Likewise, the metamethod may not call a Haskell function unless the library was compiled without allow-unsafe-gc.

https://www.lua.org/manual/5.3/manual.html#lua_gettable.

Similar to lua_settable, but does a raw assignment (i.e., without metamethods).

https://www.lua.org/manual/5.3/manual.html#lua_rawset.

Does the equivalent of t[i] = v, where t is the table at the given index and v is the value at the top of the stack.

This function pops the value from the stack. The assignment is raw, that is, it does not invoke the __newindex metamethod.

https://www.lua.org/manual/5.3/manual.html#lua_rawseti.

Pops a table from the stack and sets it as the new metatable for the value at the given index.

https://www.lua.org/manual/5.3/manual.html#lua_setmetatable.

Pops a value from the stack and sets it as the new value associated to the full userdata at the given index.

https://www.lua.org/manual/5.3/manual.html#lua_setuservalue

Pops a value from the stack and sets it as the new value of global name.

WARNING: lua_setglobal is unsafe in Haskell: if the call to a metamethod triggers an error, then that error cannot be handled and will lead to an unrecoverable program crash. Consider using the hslua_setglobal ersatz function instead. Likewise, the global metamethod may not call a Haskell function unless the library was compiled without allow-unsafe-gc.

https://www.lua.org/manual/5.3/manual.html#lua_setglobal.

Does the equivalent to t[k] = v, where t is the value at the given index, v is the value at the top of the stack, and k is the value just below the top.

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 §2.4).

WARNING: lua_settable is unsafe in Haskell: if the call to a metamethod triggers an error, then that error cannot be handled and will lead to an unrecoverable program crash. Consider using the hslua_settable ersatz function instead. Likewise, the metamethod may not call a Haskell function unless the library was compiled without allow-unsafe-gc.

https://www.lua.org/manual/5.3/manual.html#lua_settable

Converts the zero-terminated string s 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 §3.1). 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.)

https://www.lua.org/manual/5.3/manual.html#lua_stringtonumber.

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).

The value of op must be one of the following constants:

• LUA_OPADD: performs addition (+)
• LUA_OPSUB: performs subtraction (-)
• LUA_OPMUL: performs multiplication (*)
• LUA_OPDIV: performs float division (/)
• LUA_OPIDIV: performs floor division (//)
• LUA_OPMOD: performs modulo (%)
• LUA_OPPOW: performs exponentiation (^)
• LUA_OPUNM: performs mathematical negation (unary -)
• LUA_OPBNOT: performs bitwise NOT (~)
• LUA_OPBAND: performs bitwise AND (&)
• LUA_OPBOR: performs bitwise OR (|)
• LUA_OPBXOR: performs bitwise exclusive OR (~)
• LUA_OPSHL: performs left shift (<<)
• LUA_OPSHR: performs right shift (>>)

WARNING: lua_arith is unsafe in Haskell: if the call to a metamethod triggers an error, then that error cannot be handled and will lead to an unrecoverable program crash. Consider using the hslua_arith ersatz function instead. Likewise, the metamethod may not call a Haskell function unless the library was compiled without allow-unsafe-gc.

https://www.lua.org/manual/5.3/manual.html#lua_arith.

Concatenates the n values at the top of the stack, pops them, and leaves the result at the top. If n is 1, the result is the single value on the stack (that is, the function does nothing); if n is 0, the result is the empty string. Concatenation is performed following the usual semantics of Lua (see §3.4.6 of the Lua manual).

WARNING: lua_concat is unsafe in Haskell: This function will cause an unrecoverable crash an error if any of the concatenated values causes an error when executing a metamethod. Consider using the hslua_concat ersatz function instead.

Pops a key from the stack, and pushes a key–value pair from the table at the given index (the "next" pair after the given key). If there are no more elements in the table, then lua_next returns FALSE (and pushes nothing).

A typical traversal looks like this:

-- table is in the stack at index 't'
lua_pushnil l    -- first key
let loop = lua_next l t >>= \case
      FALSE -> return ()
      _ -> do
        lua_type l (-2) >>= lua_typename l >>= peekCString >>= putStrLn
        lua_type l (-1) >>= lua_typename l >>= peekCString >>= putStrLn
        -- removes 'value'; keeps 'key' for next iteration
        lua_pop l 1
        loop
loop

While traversing a table, do not call lua_tolstring directly on a key, unless you know that the key is actually a string. Recall that lua_tolstring may change the value at the given index; this confuses the next call to lua_next.

See function next for the caveats of modifying the table during its traversal.

WARNING: lua_next is unsafe in Haskell: This function will cause an unrecoverable crash an error if the given key is neither nil nor present in the table. Consider using the hslua_next ersatz function instead.

Calls a function in protected mode.

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 lua_pcall; nargs 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 nresults, unless nresults is LUA_MULTRET. 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.

If there is any error, lua_pcall catches it, pushes a single value on the stack (the error message), and returns the error code. lua_pcall always removes the function and its arguments from the stack.

If msgh is 0, then the error object returned on the stack is exactly the original error object. Otherwise, msgh is the location of a message handler. (This index cannot be a pseudo-index.) In case of runtime errors, this function will be called with the error object and its return value will be the object returned on the stack by lua_pcall.

Typically, the message handler is used to add more debug information to the error object, such as a stack traceback. Such information cannot be gathered after the return of lua_pcall, since by then the stack has unwound.

https://www.lua.org/manual/5.3/manual.html#lua_pcall.

Loads a Lua chunk (without running it). If there are no errors, lua_load pushes the compiled chunk as a Lua function on top of the stack. Otherwise, it pushes an error message.

The return values of lua_load are:

• LUA_OK: no errors;
• LUA_ERRSYNTAX: syntax error during pre-compilation;
• LUA_ERRMEM: memory allocation error;
• LUA_ERRGCMM: error while running a __gc metamethod. (This error has no relation with the chunk being loaded. It is generated by the garbage collector.)

This function only loads a chunk; it does not run it.

lua_load automatically detects whether the chunk is text or binary, and loads it accordingly (see program luac).

The lua_load function uses a user-supplied reader function to read the chunk (see Reader). The data argument is an opaque value passed to the reader function.

The chunkname argument gives a name to the chunk, which is used for error messages and in debug information (see §4.9).

lua_load automatically detects whether the chunk is text or binary and loads it accordingly (see program luac). The string mode works as in function load, with the addition that a NULL value is equivalent to the string "bt".

lua_load uses the stack internally, so the reader function must always leave the stack unmodified when returning.

https://www.lua.org/manual/5.3/manual.html#lua_load.

Returns the status of this Lua thread.

The status can be LUA_OK for a normal thread, an error value if the thread finished the execution of a lua_resume with an error, or LUA_YIELD if the thread is suspended.

You can only call functions in threads with status LUA_OK. You can resume threads with status LUA_OK (to start a new coroutine) or LUA_YIELD (to resume a coroutine).

https://www.lua.org/manual/5.3/manual.html#lua_status.

Controls the garbage collector.

See the Lua docs at https://www.lua.org/manual/5.3/manual.html#lua_gc.

Garbage-collection options.

Stops the garbage collector.

Restarts the garbage collector.

Performs a full garbage-collection cycle.

Returns the current amount of memory (in Kbytes) in use by Lua.

Returns the remainder of dividing the current amount of bytes of memory in use by Lua by 1024.

Performs an incremental step of garbage collection.

Sets data as the new value for the pause of the collector (see §2.5) and returns the previous value of the pause.

Sets data as the new value for the step multiplier of the collector (see §2.5) and returns the previous value of the step multiplier.

Returns a boolean that tells whether the collector is running (i.e., not stopped).

Pushes the global environment onto the stack.

https://www.lua.org/manual/5.3/manual.html#lua_pushglobaltable

Pushes onto the stack the field e from the metatable of the object at index obj and returns the type of the pushed value. If the object does not have a metatable, or if the metatable does not have this field, pushes nothing and returns LUA_TNIL.

Pushes onto the stack the metatable associated with name tname in the registry (see luaL_newmetatable) (nil if there is no metatable associated with that name). Returns the type of the pushed value.

Loads a buffer as a Lua chunk. This function uses lua_load to load the chunk in the buffer pointed to by buff with size sz.

This function returns the same results as lua_load. name is the chunk name, used for debug information and error messages.

Opens all standard Lua libraries into the given state.

https://www.lua.org/manual/5.3/manual.html#luaL_openlibs

If the registry already has the key tname, returns 0. Otherwise, creates a new table to be used as a metatable for userdata, adds to this new table the pair __name = tname, adds to the registry the pair [tname] = new table, and returns 1. (The entry __name is used by some error-reporting functions.)

In both cases pushes onto the stack the final value associated with tname in the registry.

Creates and returns a reference, in the table at index t, for the object at the top of the stack (and pops the object).

A reference is a unique integer key. As long as you do not manually add integer keys into table t, luaL_ref ensures the uniqueness of the key it returns. You can retrieve an object referred by reference r by calling lua_rawgeti l t r. Function luaL_unref frees a reference and its associated object.

If the object at the top of the stack is nil, luaL_ref returns the constant LUA_REFNIL. The constant LUA_NOREF is guaranteed to be different from any reference returned by luaL_ref.

Checks whether the function argument arg is a userdata of the type tname (see luaL_newmetatable) and returns the userdata address (see lua_touserdata). Returns NULL if the test fails.

https://www.lua.org/manual/5.3/manual.html#luaL_testudata

Creates and pushes a traceback of the stack l1. If msg is not NULL it is appended at the beginning of the traceback. The level parameter tells at which level to start the traceback.

Releases reference ref from the table at index t (see luaL_ref). The entry is removed from the table, so that the referred object can be collected. The reference ref is also freed to be used again.

Key, in the registry, for table of loaded modules.

Key, in the registry, for table of preloaded loaders.

Reference to a stored value.

Value signaling that no reference was created.

Value signaling that no reference was found.

Convert a reference to its C representation.

Create a reference from its C representation.

Creates a new Lua state and set extra registry values for error bookkeeping.

Converts object to string, respecting any metamethods; returns NULL if an error occurs.

If modname is not already present in package.loaded. calls function openf with string modname as an argument and sets the call result in package.loaded[modname], as if that function has been called through require.

If glb is true, also stores the module into global modname.

Leaves a copy of the module on the stack.

Behaves like lua_gettable, but prevents unrecoverable program crashes by calling that function through lua_pcall. Takes an additional status code pointer that is set to the status returned by lua_pcall.

Behaves like lua_getglobal, but prevents unrecoverable program crashes by calling that function through lua_pcall. Takes an additional status code pointer that is set to the status returned by lua_pcall.

Behaves like lua_settable, but prevents unrecoverable program crashes by calling that function through lua_pcall. Takes an additional status code pointer that is set to the status returned by lua_pcall.

Behaves like lua_setglobal, but prevents unrecoverable program crashes by calling that function through lua_pcall. Takes an additional status code pointer that is set to the status returned by lua_pcall.

Replacement for lua_error; it uses the HsLua error signaling convention instead of raw Lua errors.

Wrapper around lua_next which catches any Lua errors.

Wrapper around lua_concat which catches any Lua errors.

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).

The value of op must be one of the following constants:

• LUA_OPADD: performs addition (+)
• LUA_OPSUB: performs subtraction (-)
• LUA_OPMUL: performs multiplication (*)
• LUA_OPDIV: performs float division (/)
• LUA_OPIDIV: performs floor division (//)
• LUA_OPMOD: performs modulo (%)
• LUA_OPPOW: performs exponentiation (^)
• LUA_OPUNM: performs mathematical negation (unary -)
• LUA_OPBNOT: performs bitwise NOT (~)
• LUA_OPBAND: performs bitwise AND (&)
• LUA_OPBOR: performs bitwise OR (|)
• LUA_OPBXOR: performs bitwise exclusive OR (~)
• LUA_OPSHL: performs left shift (<<)
• LUA_OPSHR: performs right shift (>>)

This function wraps lua_arith and takes an additional parameter status; if it is not NULL, then the return value is set to the status after calling lua_arith.

Compares two Lua values. Returns 1 if the value at index index1 satisfies op when compared with the value at index index2, following the semantics of the corresponding Lua operator (that is, it may call metamethods). Otherwise returns 0. Also returns 0 if any of the indices is not valid.

The value of op must be one of the following constants:

• LUA_OPEQ: compares for equality (==)
• LUA_OPLT: compares for less than (<)
• LUA_OPLE: compares for less or equal (<=)

This function wraps lua_compare and takes an additional parameter status; if it is not NULL, then the return value is set to the status after calling lua_compare.

Pointer to function opening the base library.

Pointer to function opening the table library.

Pointer to function opening the io library.

Pointer to function opening the os library.

Pointer to function opening the string library.

Pointer to function opening the math library.

Pointer to function opening the debug library.

Pointer to function opening the package library.

Pushes a Haskell operation as a Lua function. The Haskell operation is expected to follow the custom error protocol, i.e., it must signal errors with hslua_error.

Example

Export the function to calculate triangular numbers.

let triangular :: PreCFunction
    triangular l' = do
      n <- lua_tointegerx l' (nthBottom 1) nullPtr
      lua_pushinteger l' (sum [1..n])
      return (NumResults 1)

hslua_newhsfunction l triangular
withCString "triangular" (lua_setglobal l)