From 53bc477bbacacece64e1b569b68c6bbe36f65ca9 Mon Sep 17 00:00:00 2001 From: Ramakrishnan Muthukrishnan Date: Thu, 28 Jul 2011 22:26:24 +0530 Subject: [PATCH] adding interleave and pair procedures --- src/sicp/streams.rkt | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/src/sicp/streams.rkt b/src/sicp/streams.rkt index 42bde47..b68afe1 100644 --- a/src/sicp/streams.rkt +++ b/src/sicp/streams.rkt @@ -105,3 +105,19 @@ (stream-cdr stream))))) (define primes (sieve (integers-starting-from 2))) + +(define (interleave s1 s2) + (if (stream-null? s1) + s2 + (cons-stream (stream-car s1) + (interleave s2 (stream-cdr s1))))) + +(define (pairs s t) + (cons-stream + (list (stream-car s) (stream-car t)) + (interleave + (stream-map (lambda (x) (list (stream-car s) x)) + (stream-cdr t)) + (pairs (stream-cdr s) (stream-cdr t))))) + + -- 2.45.2