C++ Operator: Why should I use '++i' instead of 'i++'?

[Yves M]

Q: Someone told me that if I want to increment a variable and that's all, I should use ++x instead of x++. Is this true?

A: If incrementing is all that you want to do (you are not assigning the variable to something else), then yes this is a good practice, especially if you are using the increment operator on a class.

// Prefix operators are preferred in cases in the following common cases:

for (;checkstate(x);++x) dosomething(x);

++x;

For the standard data types there is usually no performance difference, but for classes there are! The reason is that (for most common implementations of) postfix operators retain a temporary copy of original variable and because the return value is returned by value, not by reference. The following code exemplifies this:

class MyClass
{
public:
    MyClass& operator++()    //Prefix increment operator  (++x)
    {
        //Perform increment operation
        return *this;
    }

    MyClass  operator++(int) //Postfix increment operator (x++)
    {
        MyClass temp = *this;
        //Perform increment operation
        return temp;
    }
};

FAQ contributed by: [Kevin Hall]