# remainder(3) — Linux manual page

```REMAINDER(3)            Linux Programmer's Manual           REMAINDER(3)
```

## NAME         top

```       drem, dremf, dreml, remainder, remainderf, remainderl - floating-
point remainder function
```

## SYNOPSIS         top

```       #include <math.h>

/* The C99 versions */
double remainder(double x, double y);
float remainderf(float x, float y);
long double remainderl(long double x, long double y);

/* Obsolete synonyms */
double drem(double x, double y);
float dremf(float x, float y);
long double dreml(long double x, long double y);

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

remainder():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| _XOPEN_SOURCE >= 500
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

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

drem(), dremf(), dreml():
/* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
```

## DESCRIPTION         top

```       These functions compute the remainder of dividing x by y.  The
return value is x-n*y, where n is the value x / y, rounded to the
nearest integer.  If the absolute value of x-n*y is 0.5, n is
chosen to be even.

These functions are unaffected by the current rounding mode (see
fenv(3)).

The drem() function does precisely the same thing.
```

## RETURN VALUE         top

```       On success, these functions return the floating-point remainder,
x-n*y.  If the return value is 0, it has the sign of x.

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

If x is an infinity, and y is not a NaN, a domain error occurs,
and a NaN is returned.

If y is zero, and x is not a NaN, a domain error occurs, and a
NaN is returned.
```

## ERRORS         top

```       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 and y is not a NaN
errno is set to EDOM (but see BUGS).  An invalid floating-
point exception (FE_INVALID) is raised.

These functions do not set errno for this case.

Domain error: y is zero
errno is set to EDOM.  An invalid floating-point exception
(FE_INVALID) is raised.
```

## ATTRIBUTES         top

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

┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface                             │ Attribute     │ Value   │
├──────────────────────────────────────┼───────────────┼─────────┤
│drem(), dremf(), dreml(),             │ Thread safety │ MT-Safe │
│remainder(), remainderf(),            │               │         │
│remainderl()                          │               │         │
└──────────────────────────────────────┴───────────────┴─────────┘
```

## CONFORMING TO         top

```       The functions remainder(), remainderf(), and remainderl() are
specified in C99, POSIX.1-2001, and POSIX.1-2008.

The function drem() is from 4.3BSD.  The float and long double
variants dremf() and dreml() exist on some systems, such as Tru64
and glibc2.  Avoid the use of these functions in favor of
remainder() etc.
```

## BUGS         top

```       Before glibc 2.15, the call

remainder(nan(""), 0);

returned a NaN, as expected, but wrongly caused a domain error.
Since glibc 2.15, a silent NaN (i.e., no domain error) is
returned.

Before glibc 2.15, errno was not set to EDOM for the domain error
that occurs when x is an infinity and y is not a NaN.
```

## EXAMPLES         top

```       The call "remainder(29.0, 3.0)" returns -1.
```

```       div(3), fmod(3), remquo(3)
```

## COLOPHON         top

```       This page is part of release 5.13 of the Linux man-pages project.
A description of the project, information about reporting bugs,