remainder, remainderf, remainderl
Defined in header <math.h>


float remainderf( float x, float y ); 
(1)  (since C99) 
double remainder( double x, double y ); 
(2)  (since C99) 
long double remainderl( long double x, long double y ); 
(3)  (since C99) 
Defined in header <tgmath.h>


#define remainder( x, y ) 
(4)  (since C99) 
remainderl
is called. Otherwise, if any argument has integer type or has type double, remainder
is called. Otherwise, remainderf
is called.The IEEE floatingpoint 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 nx/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
x, y    floating point values 
Return value
If successful, returns the IEEE floatingpoint remainder of the division x/y as defined above.
If a domain error occurs, an implementationdefined 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 floatingpoint arithmetic (IEC 60559),
 The current rounding mode has no effect.
 FE_INEXACT is never raised, the result is always exact.
 If
x
is ±∞ andy
is not NaN, NaN is returned and FE_INVALID is raised  If
y
is ±0 andx
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 floatingpoint 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 <stdio.h> #include <math.h> #include <fenv.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"); }
Output:
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
 C11 standard (ISO/IEC 9899:2011):
 7.12.10.2 The remainder functions (p: 254255)
 7.25 Typegeneric math <tgmath.h> (p: 373375)
 F.10.7.2 The remainder functions (p: 529)
 C99 standard (ISO/IEC 9899:1999):
 7.12.10.2 The remainder functions (p: 235)
 7.22 Typegeneric math <tgmath.h> (p: 335337)
 F.9.7.2 The remainder functions (p: 465)
See also
(C99) 
computes quotient and remainder of integer division (function) 
(C99)(C99) 
computes remainder of the floatingpoint division operation (function) 
(C99)(C99)(C99) 
computes signed remainder as well as the three last bits of the division operation (function) 