std::fmod,std::fmodf,std::fmodl (3) - Linux Man Pages
Defined in header <cmath>
float fmod ( float x, float y );
float fmodf( float x, float y ); (since C++11)
double fmod ( double x, double y ); (1) (2)
long double fmod ( long double x, long double y );
long double fmodl( long double x, long double y ); (3) (since C++11)
Promoted fmod ( Arithmetic1 x, Arithmetic2 y ); (4) (since C++11)
1-3) Computes the floating-point remainder of the division operation x/y.
4) A set of overloads or a function template for all combinations of arguments of arithmetic_type not covered by (1-3). If any argument has integral_type, it is cast to double. If any other argument is long double, then the return type is long double, otherwise it is double.
The floating-point remainder of the division operation x/y calculated by this function is exactly the value x - n*y, where n is x/y with its fractional part truncated.
The returned value has the same sign as x and is less than y in magnitude.
x, y - floating point values
If successful, returns the 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 (after rounding) is returned.
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),
* If x is ±0 and y is not zero, ±0 is returned
* 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 y is ±∞ and x is finite, x is returned.
* If either argument is NaN, NaN is returned
POSIX_requires that a domain error occurs if x is infinite or y is zero.
std::fmod, but not std::remainder is useful for doing silent wrapping of floating-point types to unsigned integer types: (0.0 <= (y = std::fmod( std::rint(x), 65536.0 )) ? y : 65536.0 + y) is in the range [-0.0 .. 65535.0], which corresponds to unsigned short, but std::remainder(std::rint(x), 65536.0 is in the range [-32767.0, +32768.0], which is outside of the range of signed short.
The double version of fmod behaves as if implemented as follows
The expression x - trunc(x/y)*y may not equal fmod(x,y) when the rounding of x/y to initialize the argument of trunc loses too much precision (example: x = 30.508474576271183309, y = 6.1016949152542370172)
// Run this code
lldiv computes quotient and remainder of integer division
remainderl signed remainder of the division operation
remquol signed remainder as well as the three last bits of the division operation