fmodl3

Usage

Library

Math library (libm, -lm)

Overview

These functions compute the floating-point remainder of dividing x by y. The return value is x - n * y, where n is the quotient of x / y, rounded toward zero to an integer.

To obtain the modulus, more specifically, the Least Positive Residue, you will need to adjust the result from fmod() like so:

z = fmod(x, y);
if (z < 0)
	z += fabs(y);

An alternate way to express this is with fmod(fmod(x, y) + y, y), but the second fmod() usually costs way more than the one branch.

Return value

On success, these functions return the value x - n*y, for some integer n, such that the returned value has the same sign as x and a magnitude less than the magnitude of y.

If x or y is a NaN, a NaN is returned.

If x is an infinity, a domain error occurs, and a NaN is returned.

If y is zero, a domain error occurs, and a NaN is returned.

If x is +0 (-0), and y is not zero, +0 (-0) is returned.

Errors

See math_error(7) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

Domain error: x is an infinity

errno is set to EDOM (but see BUGS). An invalid floating-point exception (FE_INVALID) is raised.

Domain error: y is zero

errno is set to EDOM. An invalid floating-point exception (FE_INVALID) is raised.

Attributes

For an explanation of the terms used in this section, see attributes(7).

Examples

The call fmod(372, 360) returns 12.

The call fmod(-372, 360) returns -12.

The call fmod(-372, -360) also returns -12.