C ++ operator overload ++

Question

which one of the two codes is right and why ?

C C::operator++() {
    x++; 
    y++; 
    return *this; 
}


C & C::operator++() {
    x++; 
    y++; 
    return *this; 
}

Thanks

They both seem to work fine, but I don't know which one is right — Ziyad Mestour, Feb 11 '14 at 17:30
The reference return is "correct" (its an lvalue thing). See [this answer](http://stackoverflow.com/questions/4421706/operator-overloading/4421719#4421719) and scroll down to the appropriate subsection. — WhozCraig, Feb 11 '14 at 17:31
As comments and answers mentiom, the second is "more" correct. PS: to whomever downvoted the question, please mention why. It's a well-formed and interesting question and does not deserve a negative score. — David Titarenco, Feb 11 '14 at 17:34
Maybe the question was downvoted because it doesn't show any research effort — anatolyg, Feb 11 '14 at 17:35
This is not a question about research, as use of `&` is a point of contention, especially in examples like above. Also, consider the OP's second post in which he said that he compiled both but wasn't sure which one is correct -- given that the answer is nontrivial (and involved in the muddy topic known as idiomatic C++ and lvalue/rvalue semantics), I'd say OP did as much research as would be required before asking the question. I guess I'm just a bit irked at SO's recent "reddit mentality" of downvote first, ask questions later. — David Titarenco, Feb 11 '14 at 17:58
While baking one's noodle on these, you can add in thoughts on `C& operator ++()&;` — WhozCraig, Feb 11 '14 at 18:10

score 7 · Accepted Answer · answered Feb 11 '14 at 17:31

7

The second one is the idiomatic one: a parameter-less operator++ is the pre-fix increment operator, which should return a reference to self.

answered Feb 11 '14 at 17:31

juanchopanza

Which function is prefix: `operator(int)++` or `operator()++`? I know one of them takes a parameter: http://forums.codeguru.com/showthread.php?231051-C-Operator-How-to-overload-postfix-increment-and-decrement-operators – Thomas Matthews Feb 11 '14 at 20:49
@ThomasMatthews the one I said in my answer :-) – juanchopanza Feb 11 '14 at 20:50

score 4 · Answer 2 · answered Feb 11 '14 at 17:32

4

Both are "correct", but the second is idiomatic, because it's expected that the prefix operator ++ returns an lvalue.

answered Feb 11 '14 at 17:32

Sebastian Redl

2 Answers2