Overload += operator if + is overloaded? [duplicate]

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Overloading += in c++

Do I need to overload the += operator if I overload + 开发者_如何转开发or will the compiler know what to do?

Thanks.

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You need to overload both.

However, if you reverse the order you can reuse your code:

struct foo
{
    // this is the "core" operation, because it's mutating (changes this)
    foo& operator+=(const foo&)
    {
        // ...
        return *this;
    }

};

foo operator+(const foo& lhs, const foo& rhs)
{
    foo ret = lhs;
    ret += rhs;        
    return ret;
}

You make a copy, operate on that copy, and return it.