From octave-sources-request at bevo dot che dot wisc dot edu  Sun Jul 23 21:43:34 2000
Subject: Patch for nan/inf support without HAVE_*...
From: Edward Jason Riedy <ejr at EECS dot Berkeley dot EDU>
To: octave-sources at bevo dot che dot wisc dot edu
Date: Sun, 23 Jul 2000 19:43:31 -0700

The appended patch should define xisnan, xfinite, and xisinf 
reasonably on all platforms Octave seems to support.  An
over-optimizing compiler will reduce the tests to the ones in
the current code, so it should be no worse than at present.

The only potential problem I can see is if overflow traps.
Then the 2.0 * x tests may trap when x has the largest
possible exponent on radix-2 floating point machines.

I've generally enabled setting octave_Inf and octave_NaN 
through calculation.  If ``[s]ome version of gcc on some old 
version of Linux used to crash'', well, people should upgrade.

Also, many of the HAVE_ISNAN, etc. tests are superfluous even
without my changes.  Since xisnan is currently hard-wired to
return false, you needn't worry about returning the undefined
octave_NaN.

This passes tests on my machine after manually undefining the
right pieces of config.h.  I have a PPro, so that's not
surprising.  One test does fail the suite (residue-1.m), but
it returns the correct answer when run by hand.  Likely a
dejagnu version mismatch or something like that.

Jason

--- liboctave/lo-mappers.cc.orig	Sun Jul 23 18:32:06 2000
+++ liboctave/lo-mappers.cc	Sun Jul 23 18:43:36 2000
 at @ -65,11 +65,7 @@
   if (x < 0.0)
     return M_PI;
   else
-#if defined (HAVE_ISNAN)
     return xisnan (x) ? octave_NaN : 0.0;
-#else
-    return 0.0;
-#endif
 }
 
 double
 at @ -87,11 +83,7 @@
 double
 imag (double x)
 {
-#if defined (HAVE_ISNAN)
   return xisnan (x) ? octave_NaN : 0.0;
-#else
-  return 0.0;
-#endif
 }
 
 double
 at @ -115,11 +107,7 @@
   else if (x > 0.0)
     tmp = 1.0;
 
-#if defined (HAVE_ISNAN)
   return xisnan (x) ? octave_NaN : tmp;
-#else
-  return tmp;
-#endif
 }
 
 double
 at @ -152,7 +140,12 @@
 #if defined (HAVE_ISNAN)
   return isnan (x) != 0;
 #else
-  return false;
+  /*
+    Testing NaN == NaN returns false under arithmetics conforming to
+    IEEE 754.  An over-zealous compiler may optimize x == x to true.
+    That is no worse than the ``return false'' which !(x==x) replaced.
+  */
+  return !(x == x);
 #endif
 }
 
 at @ -164,7 +157,13 @@
 #elif defined (HAVE_ISINF) && defined (HAVE_ISNAN)
   return (! isinf (x) && ! isnan (x));
 #else
-  return true;
+  double tmp = 2.0 * x;
+  /* 
+    Twice +/- infinity is still +/- infinity.  Again, an over-zealous
+    compiler will reduce this to ``return true''.  That was the previous
+    result returned.
+  */
+  return (tmp != x);
 #endif
 }
 
 at @ -176,7 +175,9 @@
 #elif defined (HAVE_FINITE) && defined (HAVE_ISNAN)
   return (! (finite (x) || isnan (x)));
 #else
-  return false;
+  // See comment in xfinite
+  double tmp = 2.0 * x;
+  return (tmp == x);
 #endif
 }
 
 at @ -291,11 +292,7 @@
 bool
 xisnan (const Complex& x)
 {
-#if defined (HAVE_ISNAN)
-  return (isnan (real (x)) || isnan (imag (x)));
-#else
-  return false;
-#endif
+  return (xisnan (real (x)) || xisnan (imag (x)));
 }
 
 bool
--- liboctave/lo-ieee.cc.orig	Sun Jul 23 18:39:38 2000
+++ liboctave/lo-ieee.cc	Sun Jul 23 18:40:11 2000
 at @ -56,8 +56,6 @@
 void
 octave_ieee_init (void)
 {
-#if defined (HAVE_ISINF) || defined (HAVE_FINITE)
-
 // Some version of gcc on some old version of Linux used to crash when
 // trying to make Inf and NaN.
 
 at @ -79,17 +77,11 @@
     }
 #endif
 
-#endif
-
-#if defined (HAVE_ISNAN)
-
 #if defined (__alpha__) && ! defined (linux)
   extern unsigned int DQNAN[2];
   octave_NaN = (*(X_CAST(double *, DQNAN)));
 #else
   octave_NaN = octave_Inf / octave_Inf;
-#endif
-
 #endif
 }
 



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