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(define-module (srfi srfi-41 util)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-41)
#:use-module (util) ; let*, find-min
#:export (stream-car+cdr interleave-streams))
(define (stream-car+cdr stream)
(values (stream-car stream)
(stream-cdr stream)))
;; Merges a number of totally ordered streams into a single
;; totally ordered stream.
;; ((≺, stream)) → (≺, stream)
(define (interleave-streams < streams)
;; Drop all empty streams
(let ((streams (remove stream-null? streams)))
;; If all streams where empty, end the output stream
(if (null? streams)
stream-null
(let* ((min other (find-min < stream-car streams))
(m ms (stream-car+cdr min)))
(stream-cons m (interleave-streams < (cons ms other)))))))
;;; Varför är allting så långsamt‽‽‽‽‽‽‽‽
(define-public (filter-sorted-stream proc stream)
(stream-take-while
proc (stream-drop-while
(negate proc) stream)))
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