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'\" t
.\" Copyright 2001 Andries Brouwer <aeb@cwi.nl>.
.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
.\" <mtk.manpages@gmail.com>
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH floor 3 2024-05-02 "Linux man-pages (unreleased)"
.SH NAME
floor, floorf, floorl \- largest integral value not greater than argument
.SH LIBRARY
Math library
.RI ( libm ", " \-lm )
.SH SYNOPSIS
.nf
.B #include <math.h>
.P
.BI "double floor(double " x );
.BI "float floorf(float " x );
.BI "long double floorl(long double " x );
.fi
.P
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.P
.BR floorf (),
.BR floorl ():
.nf
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.fi
.SH DESCRIPTION
These functions return the largest integral value that is not greater than
.IR x .
.P
For example,
.I floor(0.5)
is 0.0, and
.I floor(\-0.5)
is \-1.0.
.SH RETURN VALUE
These functions return the floor of
.IR x .
.P
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;
lbx lb lb
l l l.
Interface Attribute Value
T{
.na
.nh
.BR floor (),
.BR floorf (),
.BR floorl ()
T} Thread safety MT-Safe
.TE
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
C99, POSIX.1-2001.
.P
The variant returning
.I double
also conforms to
SVr4, 4.3BSD, C89.
.P
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 127 (respectively, 1023),
and the number of mantissa bits
including the implicit bit
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)
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