Remainder

Defined in header <cmath>.

Description

The IEEE floating-point remainder of the division operation x / y calculated by this function is exactly the value x - quo * y, where the value quo is the integral value nearest the exact value x / y. When |quo-x/y| = ½, the value quo is chosen to be even.

In contrast to std::fmod, the returned value is not guaranteed to have the same sign as x.

If the returned value is zero, it will have the same sign as x.

Declarations

C++23

// 1)
constexpr /* floating-point-type */
            remainder ( /* floating-point-type */ x,
                        /* floating-point-type */ y );
// 2)
constexpr float remainderf( float x, float y );
// 3)
constexpr long double remainderl( long double x, long double y );

Additional Overloads

// 4)
template< class Arithmetic1, class Arithmetic2 >
/* common-floating-point-type */
    constexpr remainder( Arithmetic1 x, Arithmetic2 y );

C++11

// 1)
float remainder ( float x, float y );
// 2)
double remainder ( double x, double y );
// 3)
long double remainder ( long double x, long double y );
// 4)
float remainderf( float x, float y );
// 5)
long double remainderl( long double x, long double y );

Additional Overloads

// 6)
template< class Arithmetic1, class Arithmetic2 >
/* common-floating-point-type */
    remainder( Arithmetic1 x, Arithmetic2 y );

Parameters

x, y - floating-point or integer values

Return value

If successful, returns the IEEE floating-point remainder of the division x / y as defined above.

If a domain error occurs, an implementation-defined value is returned (NaN where supported)

If a range error occurs due to underflow, the correct result is returned.

If y is zero, but the domain error does not occur, zero is returned.

Error handling

Errors are reported as specified in math_errhandling.

Domain error may occur if y is zero.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

The current rounding mode has no effect. FE_INEXACT is never raised, the result is always exact.

• If x is ±∞ and y is not NaN, NaN is returned and FE_INVALID is raised
• If y is ±0 and x is not NaN, NaN is returned and FE_INVALID is raised
• If either argument is NaN, NaN is returned

Examples

#include <cfenv>
#include <cmath>
#include <iostream>
 
// #pragma STDC FENV_ACCESS ON
 
int main()
{
    std::cout 
        << "remainder(+5.1, +3.0) = " 
        << std::remainder(5.1, 3) << '\n'
        << "remainder(-5.1, +3.0) = " 
        << std::remainder(-5.1, 3) << '\n'
        << "remainder(+5.1, -3.0) = " 
        << std::remainder(5.1, -3) << '\n'
        << "remainder(-5.1, -3.0) = " 
        << std::remainder(-5.1, -3) << '\n';
 
    // special values
    std::cout 
        << "remainder(-0.0, 1.0) = " 
        << std::remainder(-0.0, 1) << '\n'
        << "remainder(5.1, Inf) = " 
        << std::remainder(5.1, INFINITY) << '\n';
 
    // error handling
    std::feclearexcept(FE_ALL_EXCEPT);
    std::cout 
        << "remainder(+5.1, 0) = " 
        << std::remainder(5.1, 0) << '\n';
    if (fetestexcept(FE_INVALID))
        std::cout 
            << "FE_INVALID raised\n";
}

Possible Result

remainder(+5.1, +3.0) = -0.9
remainder(-5.1, +3.0) = 0.9
remainder(+5.1, -3.0) = -0.9
remainder(-5.1, -3.0) = 0.9
remainder(-0.0, 1.0) = -0
remainder(5.1, Inf) = 5.1
remainder(+5.1, 0) = -nan
FE_INVALID raised