utils: Add 'every*'.

* guix/build/gnu-build-system.scm (every*): Move to...
* guix/build/utils.scm (every*): ... here.  New procedure.

1 files changed, 14 insertions, 0 deletions

diff --git a/guix/build/utils.scm b/guix/build/utils.scm
index 971929621a..e3f9edc5b5 100644
--- a/guix/build/utils.scm
+++ b/guix/build/utils.scm
@@ -59,10 +59,12 @@
             list->search-path-as-string
             which
 
+            every*
             alist-cons-before
             alist-cons-after
             alist-replace
             modify-phases
+
             with-atomic-file-replacement
             substitute
             substitute*
@@ -454,6 +456,18 @@ PROGRAM could not be found."
 ;;; phases.
 ;;;
 
+(define (every* pred lst)
+  "This is like 'every', but process all the elements of LST instead of
+stopping as soon as PRED returns false.  This is useful when PRED has side
+effects, such as displaying warnings or error messages."
+  (let loop ((lst    lst)
+             (result #t))
+    (match lst
+      (()
+       result)
+      ((head . tail)
+       (loop tail (and (pred head) result))))))
+
 (define* (alist-cons-before reference key value alist
                             #:optional (key=? equal?))
   "Insert the KEY/VALUE pair before the first occurrence of a pair whose key