floor(3) -- Linux man page

 

NAME

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

SYNOPSIS

#include <math.h>

double floor(double x);

float floorf(float x);
long double floorl(long double x);
 

DESCRIPTION

These functions round x down to the nearest integer.  

RETURN VALUE

The rounded integer value. If x is integral or infinite, x itself is returned.  

ERRORS

No errors other than EDOM and ERANGE can occur. If x is NaN, then NaN is returned and errno may be set to EDOM.  

NOTES

SUSv2 and POSIX 1003.1-2001 contain text about overflow (which might set errno to ERANGE, or raise an 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 (resp. 1024), and the number of mantissa bits is 24 (resp. 53).)  

CONFORMING TO

The floor() function conforms to SVID 3, POSIX, BSD 4.3, ISO 9899. The other functions are from C99.  

SEE ALSO

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