phoenix-rtos-doc / libc / functions / f / fmod.part-impl.md

fmod

Synopsis

#include <math.h>

double fmod(double x, double y);

float fmodf(float x, float y);

long double fmodl(long double x, long double y);

Status

Partially implemented

Conformance

IEEE Std 1003.1-2017

Description

These functions shall return the floating-point remainder of the division of x by y.

An application wishing to check for error situations should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred.

Return value

These functions shall return the value (x-i*y), for some integer i such that, if y is non-zero, the result has the same sign as x and magnitude less than the magnitude of y.

If the correct value would cause underflow and is not representable, a range error may occur, and fmod(), modf(), and fmodl() shall return 0.0, or (if the IEC 60559 Floating-Point option is not supported) an implementation-defined value no greater in magnitude than DBL_MIN, FLT_MIN, and LDBL_MIN, respectively.
If x or y is NaN, a NaN shall be returned, and none of the conditions below shall be considered.
If y is zero, a domain error shall occur, and a NaN shall be returned.
If x is infinite, a domain error shall occur, and a NaN shall be returned.
If x is ±0 and y is not zero, ±0 shall be returned.
If x is not infinite and y is ±Inf, x shall be returned.
If the correct value would cause underflow, and is representable, a range error may occur, and the correct value shall be returned.

Errors

These functions shall fail if:

Domain Error - The x argument is infinite or y is zero.
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to EDOM.
If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.

These functions may fail if:

Range Error - The result underflows.
If the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to ERANGE.
If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the underflow floating-point exception shall be raised.

Tests

Untested

Known bugs

None