[pure-lang-svn] SF.net SVN: pure-lang:[762] pure/trunk/lib/primitives.pure

[<ag...@us...>]

Revision: 762
          http://pure-lang.svn.sourceforge.net/pure-lang/?rev=762&view=rev
Author:   agraef
Date:     2008-09-15 05:34:59 +0000 (Mon, 15 Sep 2008)

Log Message:
-----------
Properly handle the case of IEEE 754 negative zeros.

Modified Paths:
--------------
    pure/trunk/lib/primitives.pure

Modified: pure/trunk/lib/primitives.pure
===================================================================
--- pure/trunk/lib/primitives.pure	2008-09-15 04:56:26 UTC (rev 761)
+++ pure/trunk/lib/primitives.pure	2008-09-15 05:34:59 UTC (rev 762)
@@ -125,10 +125,13 @@
 // Fractional part of x.
 frac x::int | frac x::bigint | frac x::double = x-trunc x;
 
-/* Absolute value and sign of a number. */
+/* Absolute value and sign of a number. Note that these don't distinguish
+   between IEEE 754 positive and negative zeros; abs always returns 0.0, sgn 0
+   for these. The real sign bit of a floating point zero can be obtained with
+   sgn (1/x). */
 
 abs x::int | abs x::bigint | abs x::double
-			= if x>=0 then x else -x;
+			= if x>0 then x else -x;
 sgn x::int | sgn x::bigint | sgn x::double
 			= if x>0 then 1 else if x<0 then -1 else 0;
 


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