From bbd00d2012833c6419a62f6490cbef3e896b1e11 Mon Sep 17 00:00:00 2001
From: David Thompson <dthompson2@worcester.edu>
Date: Fri, 9 Oct 2015 12:10:47 -0400
Subject: utils: Add split procedure.

* guix/utils.scm (split): New procedure.
* tests/utils.scm: Add tests.
---
 guix/utils.scm | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

(limited to 'guix/utils.scm')

diff --git a/guix/utils.scm b/guix/utils.scm
index 1d4b2ff9b0..0802a1b67a 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -3,6 +3,7 @@
 ;;; Copyright © 2013, 2014, 2015 Mark H Weaver <mhw@netris.org>
 ;;; Copyright © 2014 Eric Bavier <bavier@member.fsf.org>
 ;;; Copyright © 2014 Ian Denhardt <ian@zenhack.net>
+;;; Copyright © 2015 David Thompson <davet@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -79,6 +80,7 @@
             fold2
             fold-tree
             fold-tree-leaves
+            split
 
             filtered-port
             compressed-port
@@ -684,6 +686,23 @@ are connected to NODE in the tree, or '() or #f if NODE is a leaf node."
        (else result)))
    init children roots))
 
+(define (split lst e)
+  "Return two values, a list containing the elements of the list LST that
+appear before the first occurence of the object E and a list containing the
+elements after E."
+  (define (same? x)
+    (equal? e x))
+
+  (let loop ((rest lst)
+             (acc '()))
+    (match rest
+      (()
+       (values lst '()))
+      (((? same?) . tail)
+       (values (reverse acc) tail))
+      ((head . tail)
+       (loop tail (cons head acc))))))
+
 
 ;;;
 ;;; Source location.
-- 
cgit v1.2.3