.
Vladimir Grigoriev wrote:
However try to provide that a + a will not compute when a + b, b
+ a, and b + b will compute for two classes when one is derived
from another..
Simple, provide these three overloads and no others:
b operator+(a const& l, b const& r);
b operator+(b const& l, a const& r);
b operator+(b const& l, b const& r);
However, I can't think of a reason for this either. Think of this:
b some_b;
a& a_ref = some_b;
a_ref+a_ref; // now what?
struct c: b {...};
c some_c;
b& b_ref = some_c;
b_ref+b_ref; // and here?
Generally, operator+ is something that rather fits for value
types. Public inheritance usually means the type is rather an
entity type, which don't like being treated as a value.
Uli
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