lua_CFunction
typedef int (*lua_CFunction) (lua_State *L);

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(L) 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(L). 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.

As an example, the following function receives a variable number of numerical arguments and returns their average and sum:

     static int foo (lua_State *L) {
       int n = lua_gettop(L);    /* number of arguments */
       lua_Number sum = 0;
       int i;
       for (i = 1; i <= n; i++) {
         if (!lua_isnumber(L, i)) {
           lua_pushstring(L, "incorrect argument");
           lua_error(L);
         }
         sum += lua_tonumber(L, i);
       }
       lua_pushnumber(L, sum/n);        /* first result */
       lua_pushnumber(L, sum);         /* second result */
       return 2;                   /* number of results */
     }
EVERYTHING
Functions and Types
lua_Alloc
lua_atpanic
lua_call
lua_CFunction
lua_checkstack
lua_close
lua_concat
lua_cpcall
lua_createtable
lua_dump
lua_equal
lua_error
lua_gc
lua_getallocf
lua_getfenv
lua_getfield
lua_getglobal
lua_getmetatable
lua_gettable
lua_gettop
lua_insert
lua_Integer
lua_isboolean
lua_iscfunction
lua_isfunction
lua_islightuserdata
lua_isnil
lua_isnone
lua_isnoneornil
lua_isnumber
lua_isstring
lua_istable
lua_isthread
lua_isuserdata
lua_lessthan
lua_load
lua_newstate
lua_newtable
lua_newthread
lua_newuserdata
lua_next
lua_Number
lua_objlen
lua_pcall
lua_pop
lua_pushboolean
lua_pushcclosure
lua_pushcfunction
lua_pushfstring
lua_pushinteger
lua_pushlightuserdata
lua_pushliteral
lua_pushlstring
lua_pushnil
lua_pushnumber
lua_pushstring
lua_pushthread
lua_pushvalue
lua_pushvfstring
lua_rawequal
lua_rawget
lua_rawgeti
lua_rawset
lua_rawseti
lua_Reader
lua_register
lua_remove
lua_replace
lua_resume
lua_setallocf
lua_setfenv
lua_setfield
lua_setglobal
lua_setmetatable
lua_settable
lua_settop
lua_State
lua_status
lua_toboolean
lua_tocfunction
lua_tointeger
lua_tolstring
lua_tonumber
lua_topointer
lua_tostring
lua_tothread
lua_touserdata
lua_type
lua_typename
lua_Writer
lua_xmove
lua_yield

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