casting operator - const vs non-const

Question

I have this code sample:

class Number 
{ 
  int i;
  public:
    Number(int i1): i(i1) {}
    operator int() const {return i;}
};

What are

Answer 1

The const version can be called regardless of whether the class Number instance is const or not. If the operator is declared non-const it can only be called on non-const entities - when you try to implicitly use it where it can't be called you'll get a compile error.