From 6cf10bb9919aa27735f7d13539aaa871400777e4 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Thu, 2 Sep 2021 06:59:47 -0700
Subject: New function: delcons.

* eval.c (eval_init): Register delcons intrinsic.

* lib.[ch] (delcons): New function.

* tests/010/cons.tl: New file.

* txr.1: Documented.

* stdlib/doc-syms.tl: Updated.
---
 lib.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

(limited to 'lib.c')

diff --git a/lib.c b/lib.c
index 796853ec..68a12ae6 100644
--- a/lib.c
+++ b/lib.c
@@ -2796,6 +2796,28 @@ val tailp(val obj, val list)
   return t;
 }
 
+val delcons(val cons, val list)
+{
+  val iter = list;
+
+  if (!consp(cons))
+    return list;
+
+  if (cons == iter)
+    return cdr(iter);
+
+  while (consp(iter)) {
+    val d = us_cdr(iter);
+    if (cons == d) {
+      us_rplacd(iter, us_cdr(cons));
+      break;
+    }
+    iter = d;
+  }
+
+  return list;
+}
+
 val memq(val obj, val list)
 {
   val list_orig = list;
-- 
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