Thorsten Ottosen wrote:
I think I have found a safe way to bind a temporary to a const reference and cast away the constness.
template< class T > void is_lvalue_cast_safe( T ) {} template< class T > void is_lvalue_cast_safe( T& ) {} So, if you pass non-const rvalue the second overload can't be used and everything's OK. When passing const rvalue T will be "const" in the second overload and you get ambiguity. That's cute. I wonder if all current compilers are smart enough to not call copy constructor when passing parameter? At least all gcc versions I have, starting with 2.95 avoid the copy. When looking at: my_copy( my_sort( BOOST_LVALUE( my_unique( BOOST_LVALUE( vec() ) ) ) ), ostream_iterator<int>( cout ) ); I wish we can get away from BOOST_LVALUE too. The simple approach of: template<class T> void sort(T t) {} template<class T> void sort(T& t) {} does not really work, since there's ambiguity when passing non-const reference. It's probably possible to use mojo to distinguish non-const lvalues, const objects and non-const temporary and then add compile-time fail inside version which is selected for const objects. But we can't change definition of std::vector :-( - Volodya