Re: lua_getupvalue question

[Philipp Janda <siffiejoe@...>]

Am 03.12.2013 02:48 schröbte Andrew Starks:
> I get the upvalue. It's on the stack. It's value is 0. I want it so that
> the next time I enter the c function and retrieve the value at the same
> lua_upvalueindex address, it returns unto me the previous value, added
> to one.
>
> Please to illustrate?

    static int iter( lua_State* L ) {
      /* increment and push value to stack */
      lua_pushinteger( L, lua_tointeger( L, lua_upvalueindex( 1 ) )+1 );
      /* replace upvalue with incremented value at stack top */
      lua_replace( L, lua_upvalueindex( 1 ) );
      /* lua_replace popped the updated value, so push it again to
       * return it */
      lua_pushvalue( L, lua_upvalueindex( 1 ) );
      return 1;
    }

On the Lua side:

    > print( iter() )
    1
    > print( iter() )
    2
    > print( iter() )
    3

I hope that's what you wanted ...

> -Andrew

Philipp