C ++ Africa nan number of definitions and examples

/*

 * Definition of the C ++ Africa

NaN: each bit of the exponent 1 and mantissa are all not zero;

Infinite: Each bit exponent and the mantissa 1 are all 0; sign bit is 0, n is infinity,

1 sign bit is negative infinity. So NaN, positive infinity, negative infinity can be so defined,

So it can determine whether NaN:

//float

int __NaN=0xFFC00000,__Infinity=0x7F800000,__Neg_Infinity=0xFF800000;

const float NaN=*((float *)&__NaN),Infinity=*((float *)&__Infinity),Neg_Infinity=*((float *)&__Neg_Infinity);

bool IsNaN(float dat)

{

 int & ref=*(int *)&dat;

 return (ref&0x7F800000) == 0x7F800000 && (ref&0x7FFFFF)!=0;

}

//double

__int64 __NaN=0xFFF8000000000000,__Infinity=0x7FF0000000000000,__Neg_Infinity=0xFFF0000000000000;

const double NaN=*((double *)&__NaN),Infinity=*((double *)&__Infinity),Neg_Infinity=*((double *)&__Neg_Infinity);

bool IsNaN(double dat)

{

 __int64 & ref=*(__int64 *)&dat;

 return (ref&0x7FF0000000000000) == 0x7FF0000000000000 && (ref&0xfffffffffffff)!=0;

}

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Original link: https: //blog.csdn.net/ggjttfc/article/details/84025097

// The following example uses several non

    float xx=std::numeric_limits<float>::quiet_NaN();

    cout<<"maximum value="<<isnan(xx)<<endl;

*/