Manpages - floor.3

floor, floorf, floorl - largest integral value not greater than argument

  #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 <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

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.

For an explanation of the terms used in this section, see *attributes*(7).

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

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).)

*ceil*(3), *lrint*(3), *nearbyint*(3), *rint*(3), *round*(3), *trunc*(3)

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