I'm wanting to make sure I understand pass-by-value vs pass-by-reference properly. In particular, I'm looking at the prefix/postfix versions of the increment ++
operator for an object.
Let's suppose we have the following class X
:
class X{
private:
int i;
public:
X(){i=0;}
X& operator ++ (){ ++i; return *this; } //prefix increment
X operator ++ (int unused){ //postfix increment
X ret(*this);
i++;
return ret;
}
operator int(){ return i; } //int cast
};
First of all, have I implemented the prefix/postfix increment operators properly?
Second, how memory-efficient is the postfix operator, compared to the prefix operator? Specifically how many X
object copies are created when each version of the operator is used?
An explanation of exactly what happens with return-by-reference vs return-by-value might help me understand.
Edit: For example, with the following code...
X a;
X b=a++;
...are a and b now aliases?
It is more idiomatic to call the prefix increment of the object itself in the postfix increment:
X operator++(int)
{
X copy(*this);
++*this; // call the prefix increment
return copy;
}
The logic of incrementing an X
object is thus solely contained inside the prefix version.