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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 (date) "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)