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

From cppreference.com
< cpp‎ | numeric‎ | math
 
 
 
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cbrt
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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 cubic 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).

Contents

[edit] Parameters

arg - value of a floating-point or Integral type

[edit] Return value

If no errors occur, the cubic root of arg (3arg), is returned.

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

[edit] 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.

[edit] Notes

std::cbrt(arg) is not equivalent to std::pow(arg, 1.0/3) because the rational number
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).

[edit] 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

[edit] See also

(C++11)(C++11)
raises a number to the given power (xy)
(function) [edit]
(C++11)(C++11)
computes square root (x)
(function) [edit]
(C++11)(C++11)(C++11)
computes square root of the sum of the squares of two or three (C++17) given numbers (x2
+y2
), (x2
+y2
+z2
)
(function) [edit]