NAME

cbrt, cbrtf, cbrtl — cube root functions

SYNOPSIS

#include <math.h>

double cbrt(double x);
float cbrtf(float x);
long double cbrtl(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.1-2024 defers to the ISO C standard.

These functions shall compute the real cube root of their argument x.

RETURN VALUE

Upon successful completion, these functions shall return the cube root of x.

^[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.

EXAMPLES

None.

APPLICATION USAGE

None.

RATIONALE

For some applications, a true cube root function, which returns negative results for negative arguments, is more appropriate than pow(x, 1.0/3.0), which returns a NaN for x less than 0.

FUTURE DIRECTIONS

None.

SEE ALSO

XBD <math.h>

CHANGE HISTORY

First released in Issue 4, Version 2.

Issue 5

Moved from X/OPEN UNIX extension to BASE.

Issue 6

The cbrt() function is no longer marked as an extension.

The cbrtf() and cbrtl() 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.