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2017-09-15
Aliases: floorf(3), floorf(3), floorf(3), floorf(3), floorf(3), floorf(3), floorf(3), floorf(3), floorf(3), floorf(3), floorf(3), floorf(3), floorl(3), floorl(3), floorl(3), floorl(3), floorl(3), floorl(3), floorl(3), floorl(3), floorl(3), floorl(3), floorl(3), floorl(3)

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Linux kernel and C library user-space interface documentation

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():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

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).
Interface Attribute Value
Thread safety MT-Safe

CONFORMING TO

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