Answer 3.66

util.scm

@@ -74,6 +74,13 @@
     (cons (stream-car xs)
           (take (- n 1) (stream-cdr xs)))))
 
+(define (find item stream)
+  (define (iter n stream)
+    (if (equal? (stream-car stream) item)
+      n
+      (iter (+ n 1) (stream-cdr stream))))
+  (iter 0 stream))
+
 (define (display-stream s)
   (stream-for-each display-line s))
 
@@ -97,4 +104,8 @@
 (define (add-streams s1 s2)
   (stream-map + s1 s2))
 
+(define ones (cons-stream 1 ones))
+
+(define integers (cons-stream 1 (add-streams ones integers)))
+
 'util-loaded