diff options
| -rw-r--r-- | README.md | 26 |
1 files changed, 26 insertions, 0 deletions
@@ -423,7 +423,33 @@ letting you not have to think about how generators work. You need only remember the rule: Generators Are Consumed At Most Once. +### But Resumable Generators are Possible +An exception to the above comes in the form of *resumable* generators. +To make a resumable generator call `(make-resumable! <gen>)` on a +generator. Once you have passed a resumable generator to a consuming +form you can still get some values out of it by passing it to +`resume!`, which will create a brand new generator that picks up where +the old one left off. + +E.g. + +``` lisp + +> (defvar *resumable-evens* + (make-resumable! (filter! 'evenp (range :from 1)))) +*RESUMABLE-EVENS* + +> (take 10 *resumable-evens* ) +(2 4 6 8 10 12 14 16 18 20) + +> (setf *resumable-evens* (resume! *resumable-evens*)) +#<RESUMABLE-GENERATOR! {10049A7F63}> + +> (take 10 *resumable-evens*) +(22 24 26 28 30 32 34 36 38 40) + +``` ### The Accumulating Consumer |