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-rw-r--r--promise.scm15
1 files changed, 9 insertions, 6 deletions
diff --git a/promise.scm b/promise.scm
index f38aebf..44ffea1 100644
--- a/promise.scm
+++ b/promise.scm
@@ -1,5 +1,5 @@
;;;"promise.scm" promise for force and delay
-;;; From Revised^4 Report on the Algorithmic Language Scheme
+;;; From Revised^5 Report on the Algorithmic Language Scheme
;;; Editors: William Clinger and Jonathon Rees
;
; We intend this report to belong to the entire Scheme community, and so
@@ -7,9 +7,9 @@
; particular, we encourage implementors of Scheme to use this report as
; a starting point for manuals and other documentation, modifying it as
; necessary.
-
-(define promise:force (lambda (object) (object)))
-
+;@
+(define force (lambda (object) (object)))
+;@
(define make-promise
(lambda (proc)
(let ((result-ready? #f)
@@ -23,7 +23,10 @@
(begin (set! result-ready? #t)
(set! result x)
result))))))))
-
;;; change occurences of (DELAY <expression>) to
;;; (MAKE-PROMISE (LAMBDA () <expression>))
-;;; and (define force promise:force)
+;@
+(define-syntax delay
+ (syntax-rules ()
+ ((delay expression)
+ (make-promise (lambda () expression)))))