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

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Defined in header `<cmath>`
	(1)
float cbrt ( float num ) ; double cbrt ( double num ) ; long double cbrt ( long double num ) ;			(until C++23)
/* floating-point-type / cbrt ( / floating-point-type */ num ) ;			(since C++23) (constexpr since C++26)
float cbrtf ( float num ) ;		(2)	(since C++11) (constexpr since C++26)
long double cbrtl ( long double num ) ;		(3)	(since C++11) (constexpr since C++26)
Additional overloads (since C++11)
Defined in header `<cmath>`
template < class Integer > double cbrt ( Integer num ) ;		(A)	(constexpr since C++26)

1-3) Computes the cube root of num . The library provides overloads of


          std::cbrt

for all cv-unqualified floating-point types as the type of the parameter. (since C++23)

A) Additional overloads are provided for all integer types, which are treated as double .

(since C++11)

Parameters

num

floating-point or integer value

Return value

If no errors occur, the cube root of num ( $3 \sqrt num$ ), 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 ( num ) is not equivalent to std:: pow ( num, 1.0 / 3 ) because the rational number

13

is typically not equal to 1.0 / 3 and std::pow cannot raise a negative base to a fractional exponent. Moreover, std :: cbrt ( num ) usually gives more accurate results than std:: pow ( num, 1.0 / 3 ) (see example).

The additional overloads are not required to be provided exactly as (A) . They only need to be sufficient to ensure that for their argument num of integer type, std :: cbrt ( num ) has the same effect as std :: cbrt ( static_cast < double > ( num ) ) .

Example

Run this code

#include <cmath>
#include <iomanip>
#include <iostream>
#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

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pow powf powl (C++11) (C++11)	raises a number to the given power ( \(\small{x^y}\) $x y$ ) (function)
sqrt sqrtf sqrtl (C++11) (C++11)	computes square root ( $\sqrt x$ ) (function)
hypot hypotf hypotl (C++11) (C++11) (C++11)	computes square root of the sum of the squares of two or three (since C++17) given numbers ( $\sqrt x 2 +y 2$ ) , ( $\sqrt x 2 +y 2 +z 2$ ) (since C++17) (function)
C documentation for cbrt