From 96d35184bae81888352645ad28efa279c3d5e322 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hugo=20H=C3=B6rnquist?= <hugo@lysator.liu.se>
Date: Thu, 23 Feb 2023 01:08:16 +0100
Subject: Extend `for'-macro to allow improper list elements.

---
 module/hnh/util.scm |  3 +++
 tests/test/util.scm | 10 ++++++++++
 2 files changed, 13 insertions(+)

diff --git a/module/hnh/util.scm b/module/hnh/util.scm
index ffac17bd..36b56c58 100644
--- a/module/hnh/util.scm
+++ b/module/hnh/util.scm
@@ -118,6 +118,9 @@
     ((for (<var> <vars> ...) in <collection> b1 body ...)
      (map ((@ (ice-9 match) match-lambda) [(<var> <vars> ...) b1 body ...])
           <collection>))
+    ((for (<var> <vars> ... . <tail>) in <collection> b1 body ...)
+     (map ((@ (ice-9 match) match-lambda) [(<var> <vars> ... . <tail>) b1 body ...])
+          <collection>))
     ((for <var> in <collection> b1 body ...)
      (map (lambda (<var>) b1 body ...)
           <collection>))))
diff --git a/tests/test/util.scm b/tests/test/util.scm
index c91017fc..2a171d12 100644
--- a/tests/test/util.scm
+++ b/tests/test/util.scm
@@ -49,6 +49,16 @@
   (for (x c) in (zip (iota 12) (string->list "Hello, World"))
        x))
 
+(test-equal "for with improper list elements"
+  `(3 7)
+  (for (a . b) in '((1 . 2) (3 . 4))
+       (+ a b)))
+
+(test-equal "for with longer improper list elements"
+  '(1 2 4)
+  (for (a b . c) in '((1 -1 . 1) (2 -2 . 2) (4 -4 . 4))
+       (* c (+ 1 a b))))
+
 (test-equal "procedure label"
   120
   ((label factorial (lambda (n)
-- 
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