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: [PATCH] utils: Add split procedure.
* guix/utils.scm (split): New procedure.
* tests/utils.scm: Add tests.
---
guix/utils.scm | 19 +++++++++++++++++++
tests/utils.scm | 14 ++++++++++++++
2 files changed, 33 insertions(+)
diff --git a/guix/utils.scm b/guix/utils.scm
index 1d4b2ff9b07..0802a1b67a4 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 @@ (define-module (guix utils)
fold2
fold-tree
fold-tree-leaves
+ split
filtered-port
compressed-port
@@ -684,6 +686,23 @@ (define (fold-tree-leaves proc init children roots)
(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.
diff --git a/tests/utils.scm b/tests/utils.scm
index 115868c857a..b65d6d20ba9 100644
--- a/tests/utils.scm
+++ b/tests/utils.scm
@@ -121,6 +121,20 @@ (define temp-file
'(0 1 2 3)))
list))
+(test-equal "split, element is in list"
+ '((foo) (baz))
+ (call-with-values
+ (lambda ()
+ (split '(foo bar baz) 'bar))
+ list))
+
+(test-equal "split, element is not in list"
+ '((foo bar baz) ())
+ (call-with-values
+ (lambda ()
+ (split '(foo bar baz) 'quux))
+ list))
+
(test-equal "strip-keyword-arguments"
'(a #:b b #:c c)
(strip-keyword-arguments '(#:foo #:bar #:baz)
--
GitLab