Coroutines with C functions?

[Mark Feldman <mfeldman@...>]

Is there any reason why Lua doesn't allow C functions to be used with 
coroutines directly? As far as I can tell the code only needs two small 
changes to get these to work, and one of them is the check in 
luaB_cocreate to make sure you're passing in a Lua function. It would 
mean you can pass C functions into coroutine.create, provided you handle 
the internal suspend/resume logic yourself

#define YIELD() {lua_yield(L, 0); return -1;}

static int foo(lua_State *L)
{
   static int foo_state = 0;
   switch (foo_state++)
   {
       case 0:
           lua_getglobal(L, "print");
           lua_pushstring(L, "Hello World!");
           lua_call(L, 1, 0);
           lua_yield(L, 0);
           YIELD();

       case 1:
           lua_getglobal(L, "print");
           lua_pushstring(L, "Goodbye World!");
           lua_call(L, 1, 0);   /* fallthrough */
   }

   return 1; // die
}

And then in the Lua code you do this:

local co = coroutine.create(foo)
coroutine.resume(co)        --> Hello World!
coroutine.resume(co)        --> Goodbye World!
print(coroutine.status(co))    --> dead

Does anyone else think this would be a worthwhile addition? I'm 
currently in the process of experimenting with some optimizations where 
large portions of Lua script are automatically converted to C code that 
is then statically linked  to the program. It's basically impossible to 
do this properly without adding some sort of support for C coroutines.

Mark Feldman


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