yield equivalent in C/JavaScript?

[Oren Tirosh]

On Sat, Jun 29, 2002 at 07:12:46PM +0100, Robin Becker wrote:
> Is there any way to do yielding easily in C? I have a bunch of programs
> which are normally connected together using unix pipes. I would like to
> merge them and the problem is then how to get them to communicate nicely
> using a single process.

It's possible to implement this in C using Duff's Device:

#define BEGIN_GENERATOR static int _GenState=0; \
  switch(_GenState) { \
    case 0:

#define END_GENERATOR } \
  _GenState = 0;

#define YIELD(x) _GenState=__line__; return (x); case __line__:


int generator(arguments) {

  static int foo, bar, etc;	/* Make all variables static */

  BEGIN_GENERATOR 
  for(...) {
      if(...) {
        ...
        YIELD(x)
        ...
      } else {
        ...
      }
      ...
      YIELD(y)
      ...
   }
   END_GENERATOR
}

If you want this to be reentrant use a struct passed as an argument
to the function instead of static variables.

	Oren