NAME

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

Synopsis

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

// Run this code

#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

See also

pow
powf raises a number to the given power (\(\small{x^y}\)x^y)
powl (function)
(C++11)
(C++11)
sqrt computes square root (\(\small{\sqrt{x} }\)
sqrtf √
sqrtl x)
(C++11) (function)
(C++11)
computes square root of the sum of the squares of two or three (C++17) given
numbers (\(\scriptsize{\sqrt{x^2+y^2} }\)
√
hypot x2
hypotf +y2
hypotl ), (\(\scriptsize{\sqrt{x^2+y^2+z^2} }\)
(C++11) √
(C++11) x2
(C++11) +y2
+z2
)
(function)