Isfinite

Defined in header <cmath>.

Description

Determines if the given floating point number num has finite value i.e. it is normal, subnormal or zero, but not infinite or NaN.
​The library provides overloads for all cv-unqualified floating-point types as the type of the parameter num (since C++23).
​Additional Overloads are provided for all integer types, which are treated as double.

Declarations

C++23

// 1)
constexpr bool isfinite( /* floating-point-type */ num );

Additional Overloads

// 2)
template< class Integer >
constexpr bool isfinite( Integer num );

C++11

// 1)
bool isfinite( float num );
// 2)
bool isfinite( double num );
// 3)
bool isfinite( long double num );

Additional Overloads

// 4)
template< class Integer >
bool isfinite( Integer num );

Parameters

​num - floating-point or integer value

Return value

true if num has finite value, false otherwise.

Notes

The additional overloads are not required to be provided exactly as Additional Overloads. They only need to be sufficient to ensure that for their argument num of integer type,
std::isfinite(num) has the same effect as std::isfinite(static_cast<double>(num)).

Examples

#include <cfloat>
#include <cmath>
#include <iostream>
 
int main()
{
    std::cout 
        << std::boolalpha
        << "isfinite(NaN) = " 
        << std::isfinite(NAN) << '\n'
        << "isfinite(Inf) = " 
        << std::isfinite(INFINITY) << '\n'
        << "isfinite(-Inf) = " 
        << std::isfinite(-INFINITY) << '\n'
        << "isfinite(HUGE_VAL) = " 
        << std::isfinite(HUGE_VAL) << '\n'
        << "isfinite(0.0) = " 
        << std::isfinite(0.0) << '\n'
        << "isfinite(exp(800)) = " 
        << std::isfinite(std::exp(800)) << '\n'
        << "isfinite(DBL_MIN/2.0) = " 
        << std::isfinite(DBL_MIN / 2.0) << '\n';
}

Result

isfinite(NaN) = false
isfinite(Inf) = false
isfinite(-Inf) = false
isfinite(HUGE_VAL) = false
isfinite(0.0) = true
isfinite(exp(800)) = false
isfinite(DBL_MIN/2.0) = true