CODEWITHSUNDEEP
c++
Vinícius
Vinícius

Reputation: 15718

Checking if a number is NaN fails

Given the following questions Divide by Zero Prevention and Check if it's a NaN as the examples I've written the folowing code: 

#include <cstdlib>
#include <iostream>
#include <map>
#include <windows.h>
using namespace std;
bool IsNonNan( float fVal )
{ 
     return( fVal == fVal );
}

int main(int argc, char *argv[])
{
    int nQuota = 0;
    float fZero = 3 / (float)nQuota; 
    cout << fZero << endl;
    cout << IsNonNan( fZero ) << endl;

    system("PAUSE");
    return EXIT_SUCCESS;
}

Why is IsNonNan returning true? also why would int nZero = 3 / (float)nQuota; output: -2147483648?

Upvotes: 1

Views: 252

Answers (3)

Vinicius Horta
Vinicius Horta

Reputation: 233

int nZero = 3 / (float)nQuota; outputs -2147483648 because the conversion of 0 to float is value of <= 1e-009 which is given throughout float f = 0.000000001; or less.

Upvotes: 0

dinox0r
dinox0r

Reputation: 16039

Not, is not, NaN states for "Not a Number", it means, something that can't be expressed as a number (indeterminations like 0 / 0 which mathematically speaking, don't have a numeric representation), infinity, is just that, infinities, positive or negative

To check if a float is infinity, you can use: 

inline bool IsInf(float fval)  {
    return (fval == fval) && ((fval - fval) != 0.0f);
}

Upvotes: 1

Keith Randall
Keith Randall

Reputation: 23265

3 / 0 is +INF, not NaN. Try 0 / 0.

Upvotes: 2

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