How do I detect/trap -1.#IND in C++

Question

I have tried all of my normal tricks for detecting odd numbers (NaN, QNaN,etc) and I can't seem to detect -1.#IND. Any help would be greatly appreciated.

possible duplicate of [Checking if a double (or float) is nan in C++](http://stackoverflow.com/questions/570669/checking-if-a-double-or-float-is-nan-in-c) — Alok Save, Mar 12 '12 at 14:04
Also, Note that answer by @Cheers and hth. - Alf is the correct one in the marked duplicate. — Alok Save, Mar 12 '12 at 14:04

score 3 · Accepted Answer · answered Mar 12 '12 at 14:02

3

Try this:

http://www.johndcook.com/IEEE_exceptions_in_cpp.html

answered Mar 12 '12 at 14:02

JTeagle

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score 0 · Answer 2 · answered Mar 12 '12 at 14:02

0

Have you tried comparing the number to itself:

if ( x != x )
   assert(!"nan");

or simply

assert(x==x);

What are your normal tricks?

Also, odd numbers are 1,3,5,..., as in, the opposite of even. You're talking about NaN's I assume.

answered Mar 12 '12 at 14:02

Luchian Grigore

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I have tried comparing it to itself... works for NaN, QNan, and INF... not IND... – fbl Mar 12 '12 at 14:05
@Luchian - he meant odd as in strange / not normal – JTeagle Mar 12 '12 at 17:11

Ben Cain · Answer 3 · 2012-03-26T16:36:15.600

0

union _IEEESingle
{
   float Float;
   struct
   {
      unsigned int Frac : 23;
      unsigned int Exp  : 8;
      unsigned int Sign : 1;
   } IEEE;
};    

bool isQnan(float in) 
    { 
       return(reinterpret_cast<_IEEESingle*>(&in)->IEEE.Exp == (1u << 8)-1 && 
          reinterpret_cast<_IEEESingle*>(&in)->IEEE.Frac); 
    }

edited Mar 26 '12 at 16:36

answered Mar 26 '12 at 16:23

Ben Cain

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How do I detect/trap -1.#IND in C++

3 Answers3