The Open Group Base Specifications Issue 7
IEEE Std 1003.1-2008, 2016 Edition
Copyright © 2001-2016 The IEEE and The Open Group

#### NAME

> floor, floorf, floorl - floor function

#### SYNOPSIS

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

#### DESCRIPTION

> [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.

#### RETURN VALUE

> [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.

#### ERRORS

> No errors are defined.

The following sections are informative.

#### EXAMPLES

> None.

#### APPLICATION USAGE

> 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.

#### RATIONALE

> None.

#### FUTURE DIRECTIONS

> None.

#### SEE ALSO

> ceil, feclearexcept, fetestexcept, isnan

> Treatment of Error Conditions for Mathematical Functions, <math.h>

#### CHANGE HISTORY

> First released in Issue 1. Derived from Issue 1 of the SVID.

#### Issue 5

> The DESCRIPTION is updated to indicate how an application should check for an error. This text was previously published in the APPLICATION USAGE section.

#### Issue 6

> 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.

#### Issue 7

> POSIX.1-2008, Technical Corrigendum 1, XSH/TC1-2008/0141 [346] is applied.

End of informative text.

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