const before parameter vs const after function name c++

Question

What is the difference betweeen something like this

friend Circle copy(const Circle &);

and something like this

friend          


        

Answer 1

One refers to the parameter the other to the function.

Circle copy(const Circle &);

This means that the parameter passed in cannot be changed within the function

Circle copy(Circle&) const;

The const qualified function is used for member functions and means you cannot change the data members of the object itself. The example you posted was nonsensical.

Read right-to-left

If we rewrite the first function as Circle copy(Circle const&);, which means the same thing, it becomes clear that reading right to left becomes useful. copy is a function that takes a const reference to a Circle object and returns a Circle object by reference.