# FLOOR

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

ATTRIBUTES

CONFORMING TO

NOTES

SEE ALSO

COLOPHON

## NAME

floor, floorf,
floorl − largest integral value not greater than
argument

## SYNOPSIS

**#include
<math.h>**

**double
floor(double** *x***); **

float floorf(float *x***); **

long double floorl(long double *x***);**

Link with
*−lm*.

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

**floorf**(),
**floorl**():

_BSD_SOURCE || _SVID_SOURCE ||
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;

or *cc -std=c99*

## DESCRIPTION

These functions
return the largest integral value that is not greater than
*x*.

For example,
*floor(0.5)* is 0.0, and *floor(−0.5)* is
−1.0.

## RETURN VALUE

These functions
return the floor of *x*.

If *x* is
integral, +0, −0, NaN, or an infinity, *x* itself
is returned.

## ERRORS

No errors
occur. POSIX.1-2001 documents a range error for overflows,
but see NOTES.

## ATTRIBUTES

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

## CONFORMING TO

C99,
POSIX.1-2001. The variant returning *double* also
conforms to SVr4, 4.3BSD, C89.

## NOTES

SUSv2 and
POSIX.1-2001 contain text about overflow (which might set
*errno* to **ERANGE**, or raise an
**FE_OVERFLOW** exception). In practice, the result
cannot overflow on any current machine, so this
error-handling stuff is just nonsense. (More precisely,
overflow can happen only when the maximum value of the
exponent is smaller than the number of mantissa bits. For
the IEEE-754 standard 32-bit and 64-bit floating-point
numbers the maximum value of the exponent is 128
(respectively, 1024), and the number of mantissa bits is 24
(respectively, 53).)

## SEE ALSO

**ceil**(3),
**lrint**(3), **nearbyint**(3), **rint**(3),
**round**(3), **trunc**(3)

## COLOPHON

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