Question

How to use fpclassify() function to categorizes floating point value into zero, subnormal, normal, infinite, NaN in C++

Answer 1

#include <iostream>
#include <cmath>

using namespace std;

const char *run_fpclassify(double n)
{
	switch (fpclassify(n))
	{
		case FP_INFINITE:  return "Infinite";
		case FP_NAN:       return "NaN";
		case FP_ZERO:      return "zero";
		case FP_NORMAL:    return "normal";
		case FP_SUBNORMAL: return "subnormal";
		default:           return "unknown";
	}
}

int main()
{
	cout << "fpclassify(0.0 / 1.0) = " << run_fpclassify(0.0 / 1.0) << endl;
	cout << "fpclassify(1.0 / 1.0) = " << run_fpclassify(1.0 / 1.0) << endl;
	cout << "fpclassify(1.0) = " << run_fpclassify(1.0) << endl;
	cout << "fpclassify(-0.0) = " << run_fpclassify(-0.0) << endl;

	return 0;
}


/*
run:

fpclassify(0.0 / 1.0) = zero
fpclassify(1.0 / 1.0) = normal
fpclassify(1.0) = normal
fpclassify(-0.0) = zero

*/

 

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