adding streams

Section-3.5/mit-scheme/exercise3-51.scm

@@ -0,0 +1,41 @@
+;;
+;; [working]
+;;
+
+;;
+;; Define the supporting stream procedures:
+;;
+(define (stream-enumerate-interval low high)
+  (if (> low high)
+      the-empty-stream
+      (cons-stream
+       low
+       (stream-enumerate-interval (+ low 1) high))))
+
+(define (display-line x)
+  (newline)
+  (display x))
+
+;;
+;; Define the "show" procedure:
+;;
+(define (show x)
+  (display-line x)
+  x)
+
+;;
+;; We evaluate the first expression:
+;;
+(define x (stream-map show (stream-enumerate-interval 0 10)))
+
+;; [work]
+
+;;
+;; We evaluate the second expression:
+;;
+(stream-ref x 5)
+
+;; 
+;; We evaluate the third expression:
+;;
+(stream-ref x 7)