kolam: Implement pairify function.

The pairify function will be used in later commits.

* kolam/utils.scm: New file.

1 files changed, 34 insertions, 0 deletions

diff --git a/kolam/utils.scm b/kolam/utils.scm
new file mode 100644
index 0000000..0a7954c
--- /dev/null
+++ b/kolam/utils.scm
@@ -0,0 +1,34 @@
+;;; kolam --- GraphQL implementation
+;;; Copyright © 2021 Arun Isaac <arunisaac@systemreboot.net>
+;;;
+;;; This file is part of kolam.
+;;;
+;;; kolam is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU Affero General Public License as
+;;; published by the Free Software Foundation; either version 3 of the
+;;; License, or (at your option) any later version.
+;;;
+;;; kolam is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;; Affero General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU Affero General Public
+;;; License along with kolam.  If not, see
+;;; <http://www.gnu.org/licenses/>.
+
+(define-module (kolam utils)
+  #:use-module (ice-9 match)
+  #:export (pairify))
+
+(define (pairify lst)
+  "Return a list of pairs of successive elements of LST. For example,
+
+(pairify (list 1 2 3 4 5 6))
+=> ((1 . 2) (3 . 4) (5 . 6))"
+  (match lst
+    (() '())
+    ((first second tail ...)
+     (cons (cons first second)
+           (pairify tail)))))
+