add stream' to racket/stream'

based on a pull request from Dan King

collects/racket/stream.rkt

@@ -14,6 +14,7 @@
          prop:stream
          in-stream
 
+         stream
          stream->list
          stream-length
          stream-ref
@@ -27,7 +28,14 @@
          stream-filter
          stream-add-between
          stream-count)
-  
+
+(define-syntax stream
+  (syntax-rules ()
+    ((_)
+     empty-stream)
+    ((_ hd tl ...)
+     (stream-cons hd (stream tl ...)))))
+
 (define (stream->list s)
   (for/list ([v (in-stream s)]) v))
   

collects/scribblings/reference/sequences.scrbl

@@ -595,6 +595,11 @@ The first element of the stream as produced by @racket[first-expr]
 must be a single value. The @racket[rest-expr] must produce a stream
 when it is evaluated, otherwise the @exnraise[exn:fail:contract?].}
 
+@defform[(stream expr ...)]{ 
+
+A shorthand for nested @racket[stream-cons]es ending with
+@racket[empty-stream].}
+
 @defproc[(in-stream [s stream?]) sequence?]{
   Returns a sequence that is equivalent to @racket[s].
   @speed[in-stream "streams"]}

collects/tests/racket/stream.rktl

@@ -10,6 +10,7 @@
 (test #f stream? '#(1 2))
 
 (test 1 'stream-length (stream-length (stream-cons 1 empty-stream)))
+(test 1 'stream-length (stream-length (stream 1)))
 
 (define infinite-ones (stream-cons 1 infinite-ones))
 
@@ -27,4 +28,12 @@
 (test "hello" stream-first (sequence->stream (in-producer (lambda () "hello") (void))))
 (test 65 stream-first (sequence->stream (in-port read-byte (open-input-string "A"))))
 
+(define one-to-four (stream 1 2 3 4))
+(test 1 stream-first one-to-four)
+(test 2 stream-ref one-to-four 1)
+(test 3 stream-ref one-to-four 2)
+(test 4 stream-ref one-to-four 3)
+(test 2 'stream (stream-length (stream 1 (/ 0))))
+(test 'a 'stream (stream-first (stream 'a (/ 0))))
+
 (report-errs)

doc/release-notes/racket/HISTORY.txt

@@ -2,6 +2,7 @@ Version 5.2.0.5
 Cross-module inlining of trivial functions, plus map, for-each,
  andmap, and ormap; 'compiler-hint:cross-module-inline hint
 compiler/zo-structs: added inline-variant
+racket/stream: added stream constructor
 
 Version 5.2.0.4
 Regexps are `equal?' when they have the same source [byte] string