c++ - Constructor definition with a member initializer list -

c++ - Constructor definition with a member initializer list -

i have code given me finish few things unfamiliar me. first of all, what's point of fellow member initializer in first function?

class circle { private: double r; public: circle(double radius) : r(radius) {} double get_perimeter() { homecoming 2*pi*r; } double get_radius() { homecoming get_perimeter()/2*pi; } };

and in main() function:

int main() { double radius; cin >> radius; circle c(radius); cout << c.get_radius << endl; homecoming 0; }

the circle c(radius); line makes no sense me. can narrate me few lines addressed?

circle(double radius) : r(radius) {}

the point of fellow member initializer, r(radius), initialize fellow member r, of course! line defines constructor of circle. constructor takes argument of type double , initialises fellow member r value.

circle c(radius);

this declares variable c type circle , passes radius constructor. compare std::string str("foo"); or int x(5); - these of same form.

c++