floor, floorf, floorl - floor function
double floor(double x);
float floorf(float x);
long double floorl(long double x);
[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1-2008 defers to the ISO C standard.
These functions shall compute the largest integral value not greater than x.
[MX] The result shall have the same sign as x.
Upon successful completion, these functions shall return the largest integral value not greater than x, expressed as a double, float, or long double, as appropriate for the return type of the function.
[MX] If x is NaN, a NaN shall be returned.
If x is ±0 or ±Inf, x shall be returned.
No errors are defined.
The integral value returned by these functions might not be expressible as an intmax_t. The return value should be tested before assigning it to an integer type to avoid the undefined results of an integer overflow.
These functions may raise the inexact floating-point exception if the result differs in value from the argument.
ceil, feclearexcept, fetestexcept, isnan
Treatment of Error Conditions for Mathematical Functions, <math.h>
First released in Issue 1. Derived from Issue 1 of the SVID.
The DESCRIPTION is updated to indicate how an application should check for an error. This text was previously published in the APPLICATION USAGE section.
The floorf() and floorl() functions are added for alignment with the ISO/IEC 9899:1999 standard.
The DESCRIPTION, RETURN VALUE, ERRORS, and APPLICATION USAGE sections are revised to align with the ISO/IEC 9899:1999 standard.
IEC 60559:1989 standard floating-point extensions over the ISO/IEC 9899:1999 standard are marked.
POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0141  is applied.
return to top of page