Benefits of overloading += or -= operators

Question

Recently I have done an assignment, on overloading basic functionalists(+,-,conjugate...) of complex class using templates. I had to sweat out a little to find out the proper return type, (casting to higher type), but at the end, I got it working perfectly. This is how my class looks like -

template <typename T> class complex_t
{ 
private:
    T real;
    T imaginary;

public:

complex_t(T X, T Y)
  {
    real=X;
    imaginary=Y;
  }
}

But I didnt get full marks, because I didn't implement the +=, -= etc. operators. Why is it important to implement those operators? Whether doing that really provide any particular benefits? Can anyone share some thoughts?

Thanks in advance,

Answer 1

If you have two objects, A and B, and you want to increment A by B, without operator+=, you would do this:

A = A + B;

This will, in normal implementations, involve the creation of a third (temporary) object, which is then copied back to A. However, with operator+=, A can be modified in place, so this is normally less work, and therefore more efficient.

Perhaps more important, is that it's idiomatic to the language. C++ programmers expect that if they can do this:

A = A + B;

They can also do this:

A += B;