More efficient A=B*C; of class type? C++

Question

The expression
AA = BB * CC;
is evaluated making calling the operator* on B and C, possible code:
T operator*(const T& A, const T& B) {
T rv(A);
rv *= B;
return rv;
where *= does the 'right thing' for the type T.
Just after there is the assignment, possible code:
T& operator=(T rhs) {
rhs.swap(*this);
return *this;
Where swap() swaps (doh) without throwing exceptions.
At the moment it should goes that way:
rv is made and returned,
rv is copied in rhs,
rv is destroyed,
rhs swapped with AA,
a reference to AA is returned, but now AA contains the intended value,
rhs is destroyed, now it contains the old AA value.
Is it possible to avoid the double copy? i.e., using rv directly in the assignment?
I recall something about overloading the ternary operator, but seeking on google I find only stuff about :?, so I guess I recall wrongly.
Last edited by ezzetabi (2008-03-21 09:55:13)

Answer 1

Can you clarify for me please...  for you class T, the * operator needs to be defined but the *= operator works?  That just seems really, really strange.
Evaluation and assignment without temporaries is possible in C++ but it uses very advanced template overloading.  Look up "expression templates" if you are interested.
Also, ?: is the only ternary operator in C++.