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std::pow(std::complex)

From cppreference.com
< cpp‎ | numeric‎ | complex
 
C++
 
Numerics library
 
std::complex
Defined in header <complex>
template< class T >
std::complex<T> pow( const std::complex<T>& x, int y );
(1) (until C++11)
template< class T >
std::complex<T> pow( const std::complex<T>& x, const std::complex<T>& y );
(2)
template< class T >
std::complex<T> pow( const std::complex<T>& x, const T& y );
(3)
template< class T >
std::complex<T> pow( const T& x, const std::complex<T>& y );
(4)
Additional overloads (since C++11)
Defined in header <complex>
(A)
template< class T1, class T2 >

std::complex</* common-type */>

    pow( const std::complex<T1>& x, const std::complex<T2>& y );
(until C++23)
template< class T1, class T2 >

std::complex<std::common_type_t<T1, T2>>

    pow( const std::complex<T1>& x, const std::complex<T2>& y );
(since C++23)
(B)
template< class T, class NonComplex >

std::complex</* common-type */>

    pow( const std::complex<T>& x, const NonComplex& y );
(until C++23)
template< class T, class NonComplex >

std::complex<std::common_type_t<T, NonComplex>>

    pow( const std::complex<T>& x, const NonComplex& y );
(since C++23)
(C)
template< class T, class NonComplex >

std::complex</* common-type */>

    pow( const NonComplex& x, const std::complex<T>& y );
(until C++23)
template< class T, class NonComplex >

std::complex<std::common_type_t<T, NonComplex>>

    pow( const NonComplex& x, const std::complex<T>& y );
(since C++23)
1-4) Computes complex x raised to a complex power y with a branch cut along the negative real axis for the first argument. Non-complex arguments are treated as complex numbers with positive zero imaginary component.
A-C) Additional overloads are provided. NonComplex is not a specialization of std::complex.
(since C++11)

Contents

[edit] Parameters

x - base
y - exponent

[edit] Return value

1-4) If no errors occur, the complex power xy
, is returned.
Errors and special cases are handled as if the operation is implemented by std::exp(y * std::log(x)).
The result of std::pow(0, 0) is implementation-defined.
A-C) Same as (2-4).

[edit] Notes

Overload (1) was provided in C++98 to match the extra overloads (2) of std::pow. Those overloads were removed by the resolution of LWG issue 844.

The additional overloads are not required to be provided exactly as (A-C). They only need to be sufficient to ensure that for their first argument base and second argument exponent:

If base and/or exponent has type std::complex<T>:

  • If base and/or exponent has type std::complex<long double> or long double, then std::pow(base, exponent) has the same effect as std::pow(std::complex<long double>(base),
             std::complex<long double>(exponent)).
  • Otherwise, if base and/or exponent has type std::complex<double>, double, or an integer type, then std::pow(base, exponent) has the same effect as std::pow(std::complex<double>(base),
             std::complex<double>(exponent)).
  • Otherwise, if base and/or exponent has type std::complex<float> or float, then std::pow(base, exponent) has the same effect as std::pow(std::complex<float>(base),
             std::complex<float>(exponent)).
(until C++23)

If one argument has type std::complex<T1> and the other argument has type T2 or std::complex<T2>, then std::pow(base, exponent) has the same effect as std::pow(std::complex<std::common_type_t<T1, T2>>(base),
         std::complex<std::common_type_t<T1, T2>>(exponent))
.

If std::common_type_t<T1, T2> is not well-formed, then the program is ill-formed.

(since C++23)

[edit] Example

#include <complex>
#include <iostream>
 
int main()
{
    std::cout << std::fixed;
 
    std::complex<double> z(1.0, 2.0);
    std::cout << "(1,2)^2 = " << std::pow(z, 2) << '\n';
 
    std::complex<double> z2(-1.0, 0.0); / square root of -1
    std::cout << "-1^0.5 = " << std::pow(z2, 0.5) << '\n';
 
    std::complex<double> z3(-1.0, -0.0); / other side of the cut
    std::cout << "(-1,-0)^0.5 = " << std::pow(z3, 0.5) << '\n';
 
    std::complex<double> i(0.0, 1.0); / i^i = exp(-pi / 2)
    std::cout << "i^i = " << std::pow(i, i) << '\n';
}

Output:

(1,2)^2 = (-3.000000,4.000000)
-1^0.5 = (0.000000,1.000000)
(-1,-0)^0.5 = (0.000000,-1.000000)
i^i = (0.207880,0.000000)

[edit] See also

complex square root in the range of the right half-plane
(function template) [edit]
(C++11)(C++11)
raises a number to the given power (xy)
(function) [edit]
applies the function std::pow to two valarrays or a valarray and a value
(function template) [edit]

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