.\" Copyright 2001 Andries Brouwer <aeb@cwi.nl>.

.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk

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.\"

.TH FLOOR 3  2017-09-15 "" "Linux Programmer's Manual"

.SH NAME

floor, floorf, floorl \- largest integral value not greater than argument

.SH SYNOPSIS

.nf

.B #include <math.h>

.PP

.BI "double floor(double " x );

.BI "float floorf(float " x );

.BI "long double floorl(long double " x );

.fi

.PP

Link with \fI\-lm\fP.

.PP

.in -4n

Feature Test Macro Requirements for glibc (see

.BR feature_test_macros (7)):

.in

.PP

.ad l

.BR floorf (),

.BR floorl ():

.RS 4

_ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L

    || /* Since glibc 2.19: */ _DEFAULT_SOURCE

    || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

.RE

.ad

.SH DESCRIPTION

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

.IR x .

.PP

For example,

.IR floor(0.5)

is 0.0, and

.IR floor(\-0.5)

is \-1.0.

.SH RETURN VALUE

These functions return the floor of

.IR x .

.PP

If

.I x

is integral, +0, \-0, NaN, or an infinity,

.I x

itself is returned.

.SH ERRORS

No errors occur.

POSIX.1-2001 documents a range error for overflows, but see NOTES.

.SH ATTRIBUTES

For an explanation of the terms used in this section, see

.BR attributes (7).

.TS

allbox;

lbw27 lb lb

l l l.

Interface	Attribute	Value

T{

.BR floor (),

.BR floorf (),

.BR floorl ()

T}	Thread safety	MT-Safe

.TE

.SH CONFORMING TO

C99, POSIX.1-2001, POSIX.1-2008.

.PP

The variant returning

.I double

also conforms to

SVr4, 4.3BSD, C89.

.SH NOTES

SUSv2 and POSIX.1-2001 contain text about overflow (which might set

.I errno

to

.BR ERANGE ,

or raise an

.B FE_OVERFLOW

exception).

In practice, the result cannot overflow on any current machine,

so this error-handling stuff is just nonsense.

.\" The POSIX.1-2001 APPLICATION USAGE SECTION discusses this point.

(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).)

.SH SEE ALSO

.BR ceil (3),

.BR lrint (3),

.BR nearbyint (3),

.BR rint (3),

.BR round (3),

.BR trunc (3)

.SH COLOPHON

This page is part of release 4.15 of the Linux

.I man-pages

project.

A description of the project,

information about reporting bugs,

and the latest version of this page,

can be found at

\%https://www.kernel.org/doc/man\-pages/.