floor(3) Library Functions Manual floor(3)
NAME
floor, floorf, floorl - largest integral value not greater than argu-
ment
LIBRARY
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
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 attrib-
utes(7).
┌───────────────────────────────────────────┬───────────────┬─────────┐
│ Interface │ Attribute │ Value │
├───────────────────────────────────────────┼───────────────┼─────────┤
│ floor(), floorf(), floorl() │ 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 er-
rno 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 127 (respectively, 1023),
and the number of mantissa bits including the implicit bit is 24 (re-
spectively, 53).)
SEE ALSO
ceil(3), lrint(3), nearbyint(3), rint(3), round(3), trunc(3)
Linux man-pages 6.7 2023-10-31 floor(3)
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