is there any specific case where pass-by-value is preferred over pass-by-const-reference in C++?

Question

I read that they are conceptually equal. In practice, is there any occasion that

foo(T t) 

is preferred over

foo(const T&         


        

Answer 1

Some routines require a copy, and so should not be pass by reference. For example, a chess playing program's move generator might need a copy of the current position to work on (recursively) rather than actually modifying the original instance of the position.