operator==,!=(std::complex) - cppreference.com

From cppreference.com

Defined in header `<complex>`
template< class T > bool operator==( const complex<T>& lhs, const complex<T>& rhs );	(1)	(until C++14)
template< class T > constexpr bool operator==( const complex<T>& lhs, const complex<T>& rhs );	(1)	(since C++14)
template< class T > bool operator==( const complex<T>& lhs, const T& rhs );	(2)	(until C++14)
template< class T > constexpr bool operator==( const complex<T>& lhs, const T& rhs );	(2)	(since C++14)
template< class T > bool operator==( const T& lhs, const complex<T>& rhs );	(3)	(until C++14)
template< class T > constexpr bool operator==( const T& lhs, const complex<T>& rhs );	(3)	(since C++14) (until C++20)
template< class T > bool operator!=( const complex<T>& lhs, const complex<T>& rhs );	(4)	(until C++14)
template< class T > constexpr bool operator!=( const complex<T>& lhs, const complex<T>& rhs );	(4)	(since C++14) (until C++20)
template< class T > bool operator!=( const complex<T>& lhs, const T& rhs );	(5)	(until C++14)
template< class T > constexpr bool operator!=( const complex<T>& lhs, const T& rhs );	(5)	(since C++14) (until C++20)
template< class T > bool operator!=( const T& lhs, const complex<T>& rhs );	(6)	(until C++14)
template< class T > constexpr bool operator!=( const T& lhs, const complex<T>& rhs );	(6)	(since C++14) (until C++20)

Compares two complex numbers. Scalar arguments are treated as complex numbers with the real part equal to the argument and the imaginary part set to zero.

1-3) Compares lhs and rhs for equality.

4-6) Compares lhs and rhs for inequality.

The != operator is synthesized from operator==.

(since C++20)

Parameters

lhs, rhs - the arguments to compare: either both complex numbers or one complex and one scalar of matching type (float, double, long double)

Return value

1-3) true if respective parts of lhs are equal to rhs, false otherwise.

4-6) !(lhs == rhs)

Example

#include <complex>

int main()
{
    using std::operator""i; // or: using namespace std::complex_literals;

    static_assert(1.0i == 1.0i);
    static_assert(2.0i != 1.0i);

    constexpr std::complex z(1.0, 0.0);
    static_assert(z == 1.0);
    static_assert(1.0 == z);
    static_assert(2.0 != z);
    static_assert(z != 2.0);
}