Largest integral value not greater than argument

#include <math.h>double floor(doublex);float floorf(floatx);long double floorl(long doublex);

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*

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.

These functions return the floor of *x*.

If *x* is integral, +0, -0, NaN, or an infinity, *x* itself is returned.

No errors occur. POSIX.1-2001 documents a range error for overflows, but see NOTES.

The **floor**(), **floorf**(), and **floorl**() functions are thread-safe.

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 128 (respectively, 1024), and the number of mantissa bits is 24 (respectively, 53).)

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