remainder, remainderf, remainderl

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

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

If the returned value is ​ 0 ​ , it will have the same sign as x .

Parameters

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.

Notes

POSIX requires that a domain error occurs if x is infinite or y is zero.

fmod , but not remainder is useful for doing silent wrapping of floating-point types to unsigned integer types: ( 0.0 <= ( y = fmod ( rint ( x ) , 65536.0 ) ) ? y : 65536.0 + y ) is in the range [ - 0.0 , 65535.0 ] , which corresponds to unsigned short , but remainder ( rint ( x ) , 65536.0 ) is in the range [ - 32767.0 , + 32768.0 ] , which is outside of the range of signed short .

Example

#include <fenv.h>
#include <math.h>
#include <stdio.h>
// #pragma STDC FENV_ACCESS ON
 
int main(void)
{
    printf("remainder(+5.1, +3.0) = %.1f\n", remainder(5.1, 3));
    printf("remainder(-5.1, +3.0) = %.1f\n", remainder(-5.1, 3));
    printf("remainder(+5.1, -3.0) = %.1f\n", remainder(5.1, -3));
    printf("remainder(-5.1, -3.0) = %.1f\n", remainder(-5.1, -3));
 
    // special values
    printf("remainder(-0.0, 1.0) = %.1f\n", remainder(-0.0, 1));
    printf("remainder(+5.1, Inf) = %.1f\n", remainder(5.1, INFINITY));
 
    // error handling
    feclearexcept(FE_ALL_EXCEPT);
    printf("remainder(+5.1, 0) = %.1f\n", remainder(5.1, 0));
    if (fetestexcept(FE_INVALID))
        puts("    FE_INVALID raised");
}

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

References

See also