NAME

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

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 attributes(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 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).)

SEE ALSO

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