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std::cbrt, std::cbrtf, std::cbrtl

Defined in header `<cmath>`
float cbrt ( float arg ); float cbrtf( float arg );	(1)	(since C++11)
double cbrt ( double arg );	(2)	(since C++11)
long double cbrt ( long double arg ); long double cbrtl( long double arg );	(3)	(since C++11)
double cbrt ( IntegralType arg );	(4)	(since C++11)

1-3) Computes the cube root of arg.

4) A set of overloads or a function template accepting an argument of any integral type. Equivalent to 2) (the argument is cast to double).

Parameters

arg

value of a floating-point or Integral type

Return value

If no errors occur, the cube root of arg (\(\small{\sqrt[3]{arg} }\)3√arg), is returned.

If a range error occurs due to underflow, the correct result (after rounding) is returned.

Error handling

Errors are reported as specified in math_errhandling.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

if the argument is ±0 or ±∞, it is returned, unchanged
if the argument is NaN, NaN is returned.

Notes

std::cbrt(arg) is not equivalent to std::pow(arg, 1.0/3) because the rational number \(\small{\frac1{3} }\)1/3 is typically not equal to 1.0/3 and std::pow cannot raise a negative base to a fractional exponent. Moreover, std::cbrt(arg) usually gives more accurate results than std::pow(arg, 1.0/3) (see example).

Example

#include <iostream>
#include <iomanip>
#include <cmath>
#include <limits>
 
int main()
{
    std::cout
        << "Normal use:\n"
        << "cbrt(729)       = " << std::cbrt(729) << '\n'
        << "cbrt(-0.125)    = " << std::cbrt(-0.125) << '\n'
        << "Special values:\n"
        << "cbrt(-0)        = " << std::cbrt(-0.0) << '\n'
        << "cbrt(+inf)      = " << std::cbrt(INFINITY) << '\n'
        << "Accuracy and comparison with `pow`:\n"
        << std::setprecision(std::numeric_limits<double>::max_digits10)
        << "cbrt(343)       = " << std::cbrt(343) << '\n'
        << "pow(343,1.0/3)  = " << std::pow(343, 1.0/3) << '\n'
        << "cbrt(-343)      = " << std::cbrt(-343) << '\n'
        << "pow(-343,1.0/3) = " << std::pow(-343, 1.0/3) << '\n';
}

Possible output:

Normal use:
cbrt(729)       = 9
cbrt(-0.125)    = -0.5
Special values:
cbrt(-0)        = -0
cbrt(+inf)      = inf
Accuracy and comparison with `pow`:
cbrt(343)       = 7
pow(343,1.0/3)  = 6.9999999999999991
cbrt(-343)      = -7
pow(-343,1.0/3) = -nan

powpowfpowl (C++11)(C++11)	raises a number to the given power (\(\small{x^y}\)x^y) (function)
sqrtsqrtfsqrtl (C++11)(C++11)	computes square root (\(\small{\sqrt{x} }\)√x) (function)
hypothypotfhypotl (C++11)(C++11)(C++11)	computes square root of the sum of the squares of two or three (C++17) given numbers (\(\scriptsize{\sqrt{x^2+y^2} }\)√x2 +y2 ), (\(\scriptsize{\sqrt{x^2+y^2+z^2} }\)√x2 +y2 +z2 ) (function)
C documentation for `cbrt`