slot-ref, slot-set! et al bypass "using-class" variants

[bpt/guile.git] / module / srfi / srfi-45.scm

diff --git a/module/srfi/srfi-45.scm b/module/srfi/srfi-45.scm
index f865f91..6f7ba7e 100644 (file)
--- a/module/srfi/srfi-45.scm
+++ b/module/srfi/srfi-45.scm
@@ -25,8 +25,8 @@
 
 ;;; Commentary:
 
-;; This is the code of the reference implementation of SRFI-45,
-;; modified to use SRFI-9 and to support multiple values.
+;; This is the code of the reference implementation of SRFI-45, modified
+;; to use SRFI-9 and to add 'promise?' to the list of exports.
 
 ;; This module is documented in the Guile Reference Manual.
 
@@ -39,7 +39,8 @@
              eager
              promise?)
   #:replace (delay force promise?)
-  #:use-module (srfi srfi-9))
+  #:use-module (srfi srfi-9)
+  #:use-module (srfi srfi-9 gnu))
 
 (cond-expand-provide (current-module) '(srfi-45))
 
@@ -53,18 +54,16 @@
 (define-syntax-rule (lazy exp)
   (make-promise (make-value 'lazy (lambda () exp))))
 
-(define (eager . xs)
-  (make-promise (make-value 'eager xs)))
+(define (eager x)
+  (make-promise (make-value 'eager x)))
 
 (define-syntax-rule (delay exp)
-  (lazy (call-with-values
-            (lambda () exp)
-          eager)))
+  (lazy (eager exp)))
 
 (define (force promise)
   (let ((content (promise-val promise)))
     (case (value-tag content)
-      ((eager) (apply values (value-proc content)))
+      ((eager) (value-proc content))
       ((lazy)  (let* ((promise* ((value-proc content)))
                       (content  (promise-val promise)))        ; *
                  (if (not (eqv? (value-tag content) 'eager))   ; *
@@ -78,3 +77,17 @@
 ;; (*) These two lines re-fetch and check the original promise in case
 ;;     the first line of the let* caused it to be forced.  For an example
 ;;     where this happens, see reentrancy test 3 below.
+
+(define* (promise-visit promise #:key on-eager on-lazy)
+  (define content (promise-val promise))
+  (case (value-tag content)
+    ((eager) (on-eager (value-proc content)))
+    ((lazy)  (on-lazy (value-proc content)))))
+
+(set-record-type-printer! promise
+  (lambda (promise port)
+    (promise-visit promise
+      #:on-eager (lambda (value)
+                   (format port "#<promise = ~s>" value))
+      #:on-lazy  (lambda (proc)
+                   (format port "#<promise => ~s>" proc)))))