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std::fpclassify

From cppreference.com
< cpp‎ | numeric‎ | math
 
 
 
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fpclassify
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Defined in header <cmath>
int fpclassify( float arg );
(1) (since C++11)
int fpclassify( double arg );
(2) (since C++11)
int fpclassify( long double arg );
(3) (since C++11)
int fpclassify( IntegralType arg );
(4) (since C++11)
1-3) Categorizes floating point value arg into the following categories: zero, subnormal, normal, infinite, NAN, or implementation-defined category.
4) A set of overloads or a function template accepting the arg argument of any integral type. Equivalent to (2) (the argument is cast to double).

Contents

[edit] Parameters

arg - floating point value

[edit] Return value

one of FP_INFINITE, FP_NAN, FP_NORMAL, FP_SUBNORMAL, FP_ZERO or implementation-defined type, specifying the category of arg.

[edit] Example

#include <iostream>
#include <cmath>
#include <cfloat>
 
const char* show_classification(double x) {
    switch(std::fpclassify(x)) {
        case FP_INFINITE:  return "Inf";
        case FP_NAN:       return "NaN";
        case FP_NORMAL:    return "normal";
        case FP_SUBNORMAL: return "subnormal";
        case FP_ZERO:      return "zero";
        default:           return "unknown";
    }
}
int main()
{
    std::cout << "1.0/0.0 is " << show_classification(1/0.0) << '\n'
              << "0.0/0.0 is " << show_classification(0.0/0.0) << '\n'
              << "DBL_MIN/2 is " << show_classification(DBL_MIN/2) << '\n'
              << "-0.0 is " << show_classification(-0.0) << '\n'
              << "1.0 is " << show_classification(1.0) << '\n';
}

Output:

1.0/0.0 is Inf
0.0/0.0 is NaN
DBL_MIN/2 is subnormal
-0.0 is zero
1.0 is normal

[edit] See also

(C++11)
checks if the given number has finite value
(function) [edit]
(C++11)
checks if the given number is infinite
(function) [edit]
(C++11)
checks if the given number is NaN
(function) [edit]
(C++11)
checks if the given number is normal
(function) [edit]
provides an interface to query properties of all fundamental numeric types.
(class template) [edit]
C documentation for fpclassify