Re: Q on functions as first class values

["Michael Newberry" <mnewberry@...>]

Alex,

Yes, I understand that lua_pushstring() has no effect here. Although the 
second value was discarded, isn't sOldTitle just referencing the memory 
location of the returned value of the function SetTitle() ? That is what I 
was attempting to describe in the first message.

here's the C function (extremely simple, inside all the armor). It just 
calls another function that sets the new value and returns the previous one:

///////////////////////////////////////////////////////////////////////////////
int LuaSetTitle( struct lua_State* L )
{
   try
   {
       if ( lua_gettop( L ) == 1 )
       {
           char str[_MAX_PATH];
           strncpy( str, g_LuaScript.SetTitle( lua_tostring( L, 1 ) ), 
sizeof(str) );
           lua_pushstring( L, str );
           return 1;
       }
   }
   catch(...)
   {
   }
   lua_pushstring( L, "Default" );
   return 1;
}


Michael Newberry

----- Original Message ----- 
From: "Alex Sandro Queiroz e Silva" <ventonegro@ventonegro.org>
To: "Lua list" <lua@bazar2.conectiva.com.br>
Sent: Wednesday, February 02, 2005 12:20 PM
Subject: Re: Q on functions as first class values


> Hallo,
>
> Michael Newberry wrote:
>
> > I think I see what is happening (is this correct?):  I have assigned 
> > sOldTitle as the value of SetTitle(), so the fact that I did not update 
> > sOldTitle by the second call to SetTitle() means that sOldTitle was 
> > automatically updated by lua_pushstring() inside SetTitle(). Is this 
> > correct? If so, then I could solve the problem by using a dummy value to 
> > catch the unused return from the second call to SetTitle(). But I wonder 
> > if there is a better way; otherwise that is a "gotcha" waiting to happen 
> > again.
>
>
>     lua_pushstring just pushes a string on the stack, it's the assigment 
> that binds that string to a particular variable (sOldTitle in this case). 
> The result in the second call was probably discarded. It'd help a lot if 
> we could see the code of SetTitle().
>
> -alex
> http://www.ventonegro.org/