> On Oct 21, 2018, at 3:49 PM, Jay McCarthy <jay.mccar...@gmail.com> wrote:
>
> I think the best strategy would be to convert the generator to a
> sequence and then the sequence to a stream, then write a stream
> cartesian product. The stream will cache the results of the generator.
Nice.
#lang racket
(require racket/generator rackunit)
(define (make-cartesian-generator gens)
(generator ()
(define gstreams (for/list ([gen (in-list gens)])
(for/stream ([sol (in-producer gen
(void))])
sol)))
(let loop ([gstreams gstreams][acc empty])
(if (null? gstreams)
(yield (reverse acc))
(for ([arg (in-stream (car gstreams))])
(loop (cdr gstreams) (cons arg acc)))))))
(define g1 (generator () (yield 1) (yield 2) (void)))
(define g2 (generator () (yield 'a) (println 'only-prints-once) (yield 'b)
(void)))
(check-equal?
(for/list ([gs (in-producer (make-cartesian-generator (list g1 g2)) (void))])
gs)
'((1 a) (1 b) (2 a) (2 b)))
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