chickadee » sicp » merge

Merges two ordered streams into one ordered result stream, eliminating repetitions.

s1

Mergend

s2

Merger

(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)))))))))