01/02: memoization: (mlambda () ...) allows for inner 'define'.

[Ludovic Courtès]

civodul pushed a commit to branch master
in repository guix.

commit e3c83a7cd3618a87d74e58973dcd82e560e2da97
Author: Ludovic Courtès <address@hidden>
Date:   Sun Sep 3 23:29:11 2017 +0200

    memoization: (mlambda () ...) allows for inner 'define'.
    
    Previously (mlambda () (define foo 2) bar) would trigger a syntax error.
    
    * guix/memoization.scm (%mlambda): In the zero-argument case, move
    BODY... to a lambda to allow for inner 'define' and such.
---
 guix/memoization.scm | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/guix/memoization.scm b/guix/memoization.scm
index 5cae283..bf3b73d 100644
--- a/guix/memoization.scm
+++ b/guix/memoization.scm
@@ -76,10 +76,11 @@ the result is returned via (apply values results)."
 exactly one value."
     ((_ cached () body ...)
      ;; The zero-argument case is equivalent to a promise.
-     (let ((result #f) (cached? #f))
+     (let ((result #f) (cached? #f)
+           (compute (lambda () body ...)))
        (lambda ()
          (unless cached?
-           (set! result (begin body ...))
+           (set! result (compute))
            (set! cached? #t))
          result)))