Man page - fmodl(3)

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Manual

fmod

NAME
LIBRARY
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
STANDARDS
HISTORY
BUGS
EXAMPLES
SEE ALSO

NAME

fmod, fmodf, fmodl - floating-point remainder function

LIBRARY

Math library ( libm , -lm )

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 );

Feature Test Macro Requirements for glibc (see feature_test_macros (7)):

fmodf (), fmodl ():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

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 += 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).

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STANDARDS

C11, POSIX.1-2008.

HISTORY

C99, POSIX.1-2001.

The variant returning double also conforms to SVr4, 4.3BSD, C89.

BUGS

Before glibc 2.10, the glibc implementation did not set errno to EDOM when a domain error occurred for an infinite x .

EXAMPLES

The call fmod(372, 360) returns 348.

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

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

SEE ALSO

remainder (3)