std::complex::operator+=,-=,*=,/=

From cppreference.com
< cpp‎ | numeric‎ | complex
complex<T>& operator+=( const T& other );
(1)
template< class X >
complex<T>& operator+=( const complex<X>& other );
(2)
complex<T>& operator-=( const T& other );
(3)
template< class X >
complex<T>& operator-=( const complex<X>& other );
(4)
complex<T>& operator*=( const T& other );
(5)
template< class X >
complex<T>& operator*=( const complex<X>& other );
(6)
complex<T>& operator/=( const T& other );
(7)
template< class X >
complex<T>& operator/=( const complex<X>& other );
(8)

Implements the compound assignment operators for complex arithmetic and for mixed complex/scalar arithmetic. Scalar arguments are treated as complex numbers with the real part equal to the argument and the imaginary part set to zero.

1-2) Adds other to *this.
3-4) Subtracts other from *this.
5-6) Multiplies *this by other.
7-8) Divides *this by other.

Parameters

other - a complex or scalar value of matching type (float, double, long double)

Return value

*this

See also

applies unary operators to complex numbers
(function template)
performs complex number arithmetics on two complex values or a complex and a scalar
(function template)