Lua coding guide

4. The auxiliary library

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luaL_newmetatable

[-0, +1, m]

int luaL_newmetatable (lua_State *L, const char *tname);

If the registry already has the key tname, returns 0. Otherwise, creates a new table to be used as a metatable for userdata, adds it to the registry with key tname, and returns 1.

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

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luaL_newstate

[-0, +0, -]

lua_State *luaL_newstate (void);

Creates a new Lua state. It calls lua_newstate with an allocator based on the standard C realloc function and then sets a panic function (see lua_atpanic) that prints an error message to the standard error output in case of fatal errors.

Returns the new state, or NULL if there is a memory allocation error.

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luaL_openlibs

[-0, +0, m]

void luaL_openlibs (lua_State *L);

Opens all standard Lua libraries into the given state.

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luaL_optint

[-0, +0, v]

int luaL_optint (lua_State *L, int narg, int d);

If the function argument narg is a number, returns this number cast to an int. If this argument is absent or is nil, returns d. Otherwise, raises an error.

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luaL_optinteger

[-0, +0, v]

lua_Integer luaL_optinteger (lua_State *L,

int narg,

lua_Integer d);

If the function argument narg is a number, returns this number cast to a lua_Integer. If this argument is absent or is nil, returns d. Otherwise, raises an error.

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luaL_optlong

[-0, +0, v]

long luaL_optlong (lua_State *L, int narg, long d);

If the function argument narg is a number, returns this number cast to a long. If this argument is absent or is nil, returns d. Otherwise, raises an error.

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luaL_optlstring

[-0, +0, v]

const char *luaL_optlstring (lua_State *L,

int narg,

const char *d,

size_t *l);

If the function argument narg is a string, returns this string. If this argument is absent or is nil, returns d. Otherwise, raises an error.