Re: One more thing about Io and Lua comparison

[Steve Dekorte <steve@...>]

On Saturday, April 19, 2003, at 02:09 PM, Ignacio Castaño wrote:
> Lua binding interface is a very low level API. I haven't used Io's 
> bindings,
> but I've heard that they are very easy to use. Io is a language made 
> by a
> single person and with a small comunity, and I belive that it has more
> external libraries available than Lua. Maybe Steve can clarify this 
> better
> than me.

Hi Ignacio,

Sure. Here's what a binding for a GL function looks like:

--- Io 
--------------------------------------------------------------------

IoValue *IoGL_glVertex3d(IoGL *self, IoValue *locals, IoMessage *m)
{
  IoNumber *x = IoMessage_locals_numberArgAt_(m, locals, 0);
  IoNumber *y = IoMessage_locals_numberArgAt_(m, locals, 1);
  IoNumber *z = IoMessage_locals_numberArgAt_(m, locals, 2);
  glVertex3d(
    (GLdouble)IoNumber_asDouble(x),
    (GLdouble)IoNumber_asDouble(y),
    (GLdouble)IoNumber_asDouble(z));
  return (IoValue *)self;
}
...
Hash_at_put_(m, IOSTRING("glVertex3d"), IOCFUNCTION(IoGL_glVertex3d));

--- Lua 
--------------------------------------------------------------------

static int toluaI_gl_glVertex3d00(lua_State* tolua_S)
{
 if (
 !tolua_istype(tolua_S,1,LUA_TNUMBER,0) ||
 !tolua_istype(tolua_S,2,LUA_TNUMBER,0) ||
 !tolua_istype(tolua_S,3,LUA_TNUMBER,0) ||
 !tolua_isnoobj(tolua_S,4)
 )
 goto tolua_lerror;
 else
 {
  GLdouble x = ((GLdouble)  tolua_getnumber(tolua_S,1,0));
  GLdouble y = ((GLdouble)  tolua_getnumber(tolua_S,2,0));
  GLdouble z = ((GLdouble)  tolua_getnumber(tolua_S,3,0));
 {
  glVertex3d(x,y,z);
 }
 }
 return 0;
tolua_lerror:
 tolua_error(tolua_S,"#ferror in function 'glVertex3d'.");
 return 0;
}
...
 tolua_function(tolua_S,NULL,"glVertex3d",toluaI_gl_glVertex3d00);
-------------------------------------------------------------------

Very similar. The big difference is that Io's bindings are OO - that 
is, the glVertex3d() function is a method on an OpenGL object which 
internally holds any related state. In Lua, you add functions to Lua 
and custom userdata to hold any state associated with a binding which 
needs to be passed in with each call. (this example doesn't show that 
though as GL has static variables to hold it's state) Also, with Io 
bindings there's no stack that needs to be maintained. Arguments you 
don't use are ignored and the return argument is passed back in the 
normal way.

Cheers,
Steve
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