diff options
Diffstat (limited to 'module/srfi')
| -rw-r--r-- | module/srfi/srfi-41/util.scm | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/module/srfi/srfi-41/util.scm b/module/srfi/srfi-41/util.scm index 51671985..eda379a7 100644 --- a/module/srfi/srfi-41/util.scm +++ b/module/srfi/srfi-41/util.scm @@ -77,6 +77,18 @@ (define-public (stream->values stream) (apply values (stream->list stream))) + +;; Natural numbers from 1 and up, each number repeated 7 times. +(define-public (repeating-naturals from repeats) + (stream-unfold + cdr ; map + (const #t) ; continue? + (lambda (x) ; gen next + (if (= (1- repeats) (car x)) + (cons 0 (1+ (cdr x))) + (cons (1+ (car x)) (cdr x)))) + (cons 0 from))) + ;; Returns two values. A stream of all the elements in stream ;; which satisfiy @var{pred}, and a stream of those elements ;; that don't. @var{pred} is called once per value in the |