/
3_56.scm
26 lines (24 loc) · 1000 Bytes
/
3_56.scm
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(define (add-streams s1 s2)
(stream-map + s1 s2))
(define (mul-streams s1 s2)
(stream-map * s1 s2))
(define (scale-stream stream factor)
(stream-map (lambda (x) (* x factor)) stream))
(define ones (cons-stream 1 ones))
(define integers (cons-stream 1 (add-streams ones integers)))
(define (merge s1 s2)
(cond ((stream-null? s1) s2)
((stream-null? s2) s1)
(else
(let ((s1car (stream-car s1))
(s2car (stream-car s2)))
(cond ((< s1car s2car)
(cons-stream s1car (merge (stream-cdr s1) s2)))
((> s1car s2car)
(cons-stream s2car (merge s1 (stream-cdr s2))))
(else
(cons-stream s1car
(merge (stream-cdr s1)
(stream-cdr s2)))))))))
(define S (cons-stream 1 (merge (scale-stream S 2) (merge (scale-stream S 3)
(scale-stream S 5)))))