added unstable/future

collects/unstable/future.rkt

@@ -0,0 +1,23 @@
+#lang racket/base
+(require racket/future
+         (for-syntax racket/base))
+(provide for/async
+         for*/async)
+
+;; Note: order of touches not guaranteed.
+
+(define-syntaxes (for/async for*/async)
+  (let ()
+    (define ((transformer for/fold/derived-id) stx)
+      (syntax-case stx ()
+        [(_ (clause ...) . body)
+         (quasisyntax/loc stx
+           (let ([futures
+                  (#,for/fold/derived-id #,stx ([fs null]) (clause ...)
+                                         (cons (future (lambda () . body)) fs))])
+             ;; touches futures in original order
+             (let loop ([fs futures])
+               (cond [(pair? fs) (begin (loop (cdr fs)) (touch (car fs)))]
+                     [else (void)]))))]))
+    (values (transformer #'for/fold/derived)
+            (transformer #'for*/fold/derived))))

collects/unstable/gui/blur.rkt

@@ -6,7 +6,7 @@
          racket/draw
          racket/pretty
          racket/math
-         racket/future
+         unstable/future
          slideshow/pict)
 
 ;; TODO: use clipping regions to avoid computing unused pixels
@@ -29,14 +29,6 @@
        (exact-nonnegative-integer?)
        void?)])
 
-(define-syntax (for/async stx)
-  (syntax-case stx ()
-    [(_ (clause ...) . body)
-     #`(let ([fs
-              (for/fold/derived #,stx ([fs null]) (clause ...)
-                (cons (future (lambda () . body)) fs))])
-         (for-each touch fs))]))
-
 ;; ----
 
 (define (blur p hbr [vbr hbr] #:auto-inset? [auto-inset? #f])

collects/unstable/scribblings/future.scrbl

@@ -0,0 +1,19 @@
+#lang scribble/manual
+@(require "utils.rkt"
+          (for-label racket/base
+                     racket/future
+                     unstable/future))
+
+@title[#:tag "future"]{Futures}
+@unstable[@author+email["Ryan Culpepper" "ryanc@racket-lang.org"]]
+
+@defmodule[unstable/future]
+
+@deftogether[[
+@defform[(for/async (for-clause ...) body ...+)]
+@defform[(for*/async (for-clause ...) body ...+)]]]{
+
+Like @racket[for] and @racket[for*], but each iteration of the
+@racket[body] is executed in a separate @racket[future], and
+the futures may be @racket[touch]ed in any order.
+}

collects/unstable/scribblings/unstable.scrbl

@@ -82,6 +82,7 @@ Keep documentation and tests up to date.
 @include-section["exn.scrbl"]
 @include-section["file.scrbl"]
 @include-section["find.scrbl"]
+@include-section["future.scrbl"]
 @include-section["mutated-vars.scrbl"] ;; Finding Mutable Variables
 @include-section["function.scrbl"]
 @include-section["generics.scrbl"]