Name
floor, floorf, floorl - largest integral value not greater than argumentLibrary
Math library ( libm ", " -lm )Synopsis
#include <math.h> double floor(double x );
float floorf(float x );
long double floorl(long double x );
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 <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
Description
These functions return the largest integral value that is not greater thanx
. For example, floor(0.5) is 0.0, and floor(-0.5) is -1.0.
Return Value
These functions return the floor ofx
. 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 |
T} | Thread safety | MT-Safe |
Standards
C11, POSIX.1-2008.History
C99, POSIX.1-2001.The variant returning double also conforms to SVr4, 4.3BSD, C89.
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 127 (respectively, 1023), and the number of mantissa bits including the implicit bit is 24 (respectively, 53).)