utils: Add 'strip-keyword-arguments'.

* guix/utils.scm (strip-keyword-arguments): New procedure.
* tests/utils.scm ("strip-keyword-arguments"): New test.

2 files changed, 22 insertions, 0 deletions

diff --git a/guix/utils.scm b/guix/utils.scm
index 34a5e6c971..2814247a68 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -48,6 +48,7 @@
             compile-time-value
             fcntl-flock
             memoize
+            strip-keyword-arguments
             default-keyword-arguments
             substitute-keyword-arguments
 
@@ -424,6 +425,21 @@ exception if it's already taken."
               (hash-set! cache args results)
               (apply values results)))))))
 
+(define (strip-keyword-arguments keywords args)
+  "Remove all of the keyword arguments listed in KEYWORDS from ARGS."
+  (let loop ((args   args)
+             (result '()))
+    (match args
+      (()
+       (reverse result))
+      (((? keyword? kw) arg . rest)
+       (loop rest
+             (if (memq kw keywords)
+                 result
+                 (cons* arg kw result))))
+      ((head . tail)
+       (loop tail (cons head result))))))
+
 (define (default-keyword-arguments args defaults)
   "Return ARGS augmented with any keyword/value from DEFAULTS for
 keywords not already present in ARGS."
diff --git a/tests/utils.scm b/tests/utils.scm
index 611867ca09..a662c9a8d3 100644
--- a/tests/utils.scm
+++ b/tests/utils.scm
@@ -120,6 +120,12 @@
                '(0 1 2 3)))
     list))
 
+(test-equal "strip-keyword-arguments"
+  '(a #:b b #:c c)
+  (strip-keyword-arguments '(#:foo #:bar #:baz)
+                           '(a #:foo 42 #:b b #:baz 3
+                               #:c c #:bar 4)))
+
 (let* ((tree (alist->vhash
               '((0 2 3) (1 3 4) (2) (3 5 6) (4 6) (5) (6))
               hashq))