Libx Lua Documentation

    On this page

    C API functions and types: toboolean–typename

    lua_toboolean

    [-0, +0, –]

    int lua_toboolean (lua_State *L, int index);

    Converts the Lua value at the given index to a C boolean value (0 or 1). Like all tests in Lua, 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.)

    lua_tocfunction

    [-0, +0, –]

    lua_CFunction lua_tocfunction (lua_State *L, int index);

    Converts a value at the given index to a C function. That value must be a C function; otherwise, returns NULL.

    lua_toclose

    [-0, +0, v]

    void lua_toclose (lua_State *L, int index);

    Marks the given index in the stack as a to-be-closed slot (see §3.3.8). Like a to-be-closed variable in Lua, the value at that slot in the stack will be closed when it goes out of scope. Here, in the context of a C function, to go out of scope means that the running function returns to Lua, or there is an error, or the slot is removed from the stack through lua_settop or lua_pop, or there is a call to lua_closeslot. A slot marked as to-be-closed should not be removed from the stack by any other function in the API except lua_settop or lua_pop, unless previously deactivated by lua_closeslot.

    This function raises an error if the value at the given slot neither has a __close metamethod nor is a false value.

    This function should not be called for an index that is equal to or below an active to-be-closed slot.

    Note that, both in case of errors and of a regular return, by the time the __close metamethod runs, the C stack was already unwound, so that any automatic C variable declared in the calling function (e.g., a buffer) will be out of scope.

    lua_tointeger

    [-0, +0, –]

    lua_Integer lua_tointeger (lua_State *L, int index);

    Equivalent to lua_tointegerx with isnum equal to NULL.

    lua_tointegerx

    [-0, +0, –]

    lua_Integer lua_tointegerx (lua_State *L, int index, int *isnum);

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

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

    lua_tolstring

    [-0, +0, m]

    const char *lua_tolstring (lua_State *L, int index, size_t *len);

    Converts the Lua value at the given index to a C string. 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.)

    If len is not NULL, the function sets *len with the string length. The returned C string always has a zero (‘\0’) after its last character, but can contain other zeros in its body.

    The pointer returned by lua_tolstring may be invalidated by the garbage collector if the corresponding Lua value is removed from the stack (see §4.1.3).

    This function can raise memory errors only when converting a number to a string (as then it may create a new string).

    lua_tonumber

    [-0, +0, –]

    lua_Number lua_tonumber (lua_State *L, int index);

    Equivalent to lua_tonumberx with isnum equal to NULL.

    lua_tonumberx

    [-0, +0, –]

    lua_Number lua_tonumberx (lua_State *L, int index, int *isnum);

    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.

    lua_topointer

    [-0, +0, –]

    const void *lua_topointer (lua_State *L, int index);

    Converts the value at the given index to a generic C pointer (void*). The value can be a userdata, a table, a thread, a string, or a function; otherwise, lua_topointer returns NULL. 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.

    lua_tostring

    [-0, +0, m]

    const char *lua_tostring (lua_State *L, int index);

    Equivalent to lua_tolstring with len equal to NULL.

    lua_tothread

    [-0, +0, –]

    lua_State *lua_tothread (lua_State *L, int index);

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

    lua_touserdata

    [-0, +0, –]

    void *lua_touserdata (lua_State *L, int index);

    If the value at the given index is a full userdata, returns its memory-block address. If the value is a light userdata, returns its value (a pointer). Otherwise, returns NULL.

    lua_type

    [-0, +0, –]

    int lua_type (lua_State *L, int index);

    Returns the type of the value in the given valid index, or LUA_TNONE for a non-valid but acceptable index. The types returned by lua_type are coded by the following constants defined in lua.h: LUA_TNIL, LUA_TNUMBER, LUA_TBOOLEAN, LUA_TSTRING, LUA_TTABLE, LUA_TFUNCTION, LUA_TUSERDATA, LUA_TTHREAD, and LUA_TLIGHTUSERDATA.

    lua_typename

    [-0, +0, –]

    const char *lua_typename (lua_State *L, int tp);

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