Question

class MyClass;

int main()
{
  float a = 5;
  MyClass c1;
  MyClass c2 = a*c1;
  MyClass c3 = c1*a;
}

How can I overload the multiply operator so that both a*c1 and c1*a work?

Answer 1

Like so:

MyClass operator* (float x, const MyClass& y)
{
    //...
}

MyClass operator* (const MyClass& y, float x)
{
    //...
}

The second one can also be a member function:

class MyClass
{
    //...
    MyClass operator* (float x);
};

The first 2 options work as declarations outside of class scope.