chickadee » sicp » stream-filter

Filters a stream, applying pred.

pred

The predicate upon which to filter.

stream

The stream to filter

(define (stream-filter pred stream)
  (cond ((stream-null? stream) stream-null)
        ((pred (stream-car stream))
         (cons-stream
           (stream-car stream)
           (stream-filter pred (stream-cdr stream))))
        (else (stream-filter pred (stream-cdr stream)))))