class 内部还是外部声明？

Question

Given the following functions:

1)

IntMatrix operator+(const IntMatrix &matrix, int scalar);

2)

IntMatrix operator+(int scalar, const IntMatrix &matrix);

Which take a scalar and adds it to every member in the Matrix, Should I declare them outside the class (like what is shown above) or inside my class?

In collage they thought as that if we need it to work in both directions (symmetrical behaviour) we declare it out but here it's a little bit complicated...

Answer 1

Function 1 can be written inside the class, as a member function, but function 2 must be written as a non-member function, since the left hand side is not a IntMatrix .

I would suggest writing a operator+= that takes an int as a member function. Then you can easily call that from both operator+ , which you can write as non-members.

So your operator+ (as non-members) would look like this:

IntMatrix operator+(IntMatrix matrix, int scalar) {
  return matrix += scalar;
}

IntMatrix operator+(int scalar, IntMatrix matrix) {
  return matrix += scalar;
}