**floor**

ment
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
Multithreading (see **pthreads(7)**)
The floor(), floorf(), and floorl() functions are thread-safe.
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 man-
tissa 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)**

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