add 'infinite' generator

svn: r17552

collects/scheme/generator.ss

@@ -4,7 +4,7 @@
          scheme/control
          scheme/stxparam scheme/splicing)
 
-(provide yield generator in-generator)
+(provide yield generator in-generator infinite)
 
 ;; (define-syntax-parameter yield
 ;;   (lambda (stx)
@@ -74,6 +74,11 @@
        #'[(id ...)
           (in-producer (generator body0 body ... stop-value) stop-value)]])))
 
+(define (infinite sequence)
+  (generator
+    (for ([i (in-cycle sequence)])
+         (yield i))))
+
 #|
 ;; examples
 (for/list ([i (in-generator (for-each yield '(1 2 3)) (yield 'four))]) i)