CODEWITHSUNDEEP
c++operator-overloading
vanjoe
vanjoe

Reputation: 439

addition operator with pass by reference

I'm trying to overload the addition operator,with the following prototype:

obj operator+(obj&, obj&);

this works for a+b but triggers an error on a+b+c

g++ spits out the following error:

test.cpp:17:6: error: no match for ‘operator+’ in ‘operator+((* & a), (* & b)) + c’
test.cpp:17:6: note: candidates are:
test.cpp:10:5: note: obj operator+(obj&, obj&)
error: no match for 'operator+' in 'operator+(obj&, obj&) 
note: candidates are: obj operator+(obj&, onj&)

Upvotes: 1

Views: 118

Answers (2)

Wilson
Wilson

Reputation: 251

You can assume that the left hand side of an equation is always referring to "this" object which means you can change the signature of the overloaded operator to:

obj operator+(const obj &other){
    // Add value of "this" to value of other
    // Return obj
}

Upvotes: 0

Jonas Schäfer
Jonas Schäfer

Reputation: 20738

The problem is that your argument is a non-const reference and the operator returns a new object.

Thus, a+b evaluates to a temporary object, which cannot bind to a non-const reference as per the standard. Thus it cannot be passed as an argument to your operator+. The solution is most likely to use a const reference as @chris suggests, because you should not be modifying the operands of operator+.

No-one would expect that and thus I personally think it would be bad style to do so.

Upvotes: 3

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