From dab37a844b3fead9a85571f96d5b812d27546781 Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Sat, 17 Dec 2016 14:44:34 +0100
Subject: [PATCH] Add list-head, list-tail.

* module/mes/scm (list-head, list-tail): New function.
---
 module/mes/scm.mes | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/module/mes/scm.mes b/module/mes/scm.mes
index 2ac9180e..1b179147 100644
--- a/module/mes/scm.mes
+++ b/module/mes/scm.mes
@@ -32,6 +32,14 @@
 
 (define (list . rest) rest)
 
+(define (list-head x n)
+  (if (= 0 n) '()
+      (cons (car x) (list-head (cdr x) (- n 1)))))
+
+(define (list-tail x n)
+  (if (= 0 n) x
+      (list-tail (cdr x) (- n 1))))
+
 (define-macro (case val . args)
   (if (null? args) #f
       (let ((clause (car args)))