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

See Also

  1. Standard library functions
  2. Table of Contents