From: Eli Zaretskii <eliz@is.elta.co.il>
Date: Mon, 29 Dec 2003 13:51:54 +0000 (+0000)
Subject: (internal_equal): Return t for two NaN arguments.
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(internal_equal): Return t for two NaN arguments.
---

diff --git a/src/fns.c b/src/fns.c
index e4252c98ca5..ff40c706edd 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -2169,7 +2169,15 @@ internal_equal (o1, o2, depth)
   switch (XTYPE (o1))
     {
     case Lisp_Float:
-      return (extract_float (o1) == extract_float (o2));
+      {
+	double d1, d2;
+
+	d1 = extract_float (o1);
+	d2 = extract_float (o2);
+	/* If d is a NaN, then d != d. Two NaNs should be `equal' even
+	   though they are not =. */
+	return d1 == d2 || (d1 != d1 && d2 != d2);
+      }
 
     case Lisp_Cons:
       if (!internal_equal (XCAR (o1), XCAR (o2), depth + 1))