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std::conj(std::complex) - cppreference.com

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Defined in header <complex> 

template< class T > 
std::complex<T> conj( const std::complex<T>& z );
(1) (until C++20) 
template< class T > 
constexpr std::complex<T> conj( const std::complex<T>& z );
(since C++20)

Additional overloads (since C++11)

Defined in header <complex> 

std::complex<float>       conj( float f );
std::complex<double>      conj( double f );
std::complex<long double> conj( long double f );
(A) (until C++20) 
constexpr std::complex<float>       conj( float f );
constexpr std::complex<double>      conj( double f );
constexpr std::complex<long double> conj( long double f );
(since C++20)
(until C++23)		 
template< class FloatingPoint >
constexpr std::complex<FloatingPoint> conj( FloatingPoint f );
(since C++23) 
template< class Integer >
constexpr std::complex<double> conj( Integer i );
(B) (until C++20) 
template< class Integer >
constexpr std::complex<double> conj( Integer i );
(since C++20)

1) Computes the complex conjugate of z by reversing the sign of the imaginary part.

A,B) Additional overloads are provided for all integer and floating-point types, which are treated as complex numbers with zero imaginary component.

 (since C++11)

Parameters

z - complex value
f - floating-point value
i - integer value

Return value

1) The complex conjugate of z.

A) std::complex(f).

B) std::complex<double>(i).

Notes

The additional overloads are not required to be provided exactly as (A,B). They only need to be sufficient to ensure that for their argument num:

  • If num has a standard(until C++23) floating-point type T, then std::conj(num) has the same effect as std::conj(std::complex<T>(num)).
  • Otherwise, if num has an integer type, then std::conj(num) has the same effect as std::conj(std::complex<double>(num)).

Example

#include <complex>
#include <iostream>

int main()
{
    std::complex<double> z(1.0, 2.0);
    std::cout << "The conjugate of " << z << " is " << std::conj(z) << '\n'
              << "Their product is " << z * std::conj(z) << '\n';
}

Output: 

The conjugate of (1,2) is (1,-2)
Their product is (5,0)

See also