c++ - How to define an implicit conversion from double? -

i have defined class complex overloads + operator:

complex operator+(complex const& x, complex const& y); 

i want define implicit conversion double complex, such that, example, if write c + d, c complex , d double, call overloaded + defined above , return complex. how can this?

you need define constructor it. referred "converting constructor"

complex::complex(double x) {     // conversion } 

this allow implicit conversion, long don't use explicit keyword, force have use cast convert.

you can define other versions of operator+

complex operator+(complex const& x, double y); complex operator+(double x, complex const& y);