Hi all

I've been using OCaml for a year or so building an interpreter/compiler for the Python programming language as a research project.

It's worked pretty well for most part, but I'm trying to implement some of the features of Python involving 'lazy' features, such as generator functions and list comprehensions.

A generator in Python can be thought of as an arbitrarily generated 'lazy list'. As an example

the following is a generator capable of generating powers of 2 upto a max value.

def pow2(max):

   start = 0

   while (start .lt. max):

      yield 2^start

      start += 1

The 'yield' statement is the point where the function returns the next value and suspends itself until the next time it is 'forced'. At that time it resumes execution where it left off.

OCaml makes this particularly hard to implement this due to lack of 'control flow' features, including even a call/cc. The only way I can see right now is breaking this code down into little functions, saving the current execution environment during the suspend and keeping track of the right function to call the next time.

I've been thinking about whether I can express this in some elegant way in some lazy construct in OCaml, since this is basically a form of 'lazy' evaluation. However, I come from the C world and am not quite used to 'lazy' thinking :) Any ideas?

Raj