You can see a version of them used in srfi-41. I do believe I use them in my old implementation of rackets for loops for guile. For/foldr I used them as a way to ensure that the next iteration was evaluated only once (despite being possible to call it several times) to avoid quadratic behaviour.
I don't really think they are used that often, since when you need laziness you would probably reach for srfi-41 (which is horribly slow) or generators (srfi-158). I see them as a primitive mostly for macro writers, to be honest. It is useful if you want to handle a computation back to the user but want to make sure it is run at most one time. That is mostly how I have seen them used (and used them myself), at least. -- Linus Björnstam On Thu, 10 Jun 2021, at 07:08, Tim Meehan wrote: > Are there any good examples of "medium-sized" programs that use delay and > force? I have seen the documentation examples, but I am curious about how > it is used by other people in larger projects. >
