Scott McMurray <me22.ca+boost@gmail.com> wrote:
The problem is that the underlying type of boost::ptr_vector<T> is always vector<void*>, no matter T is const.
Since the point of this is to only ever instantiate one version of the underlying container, wouldn't it be better to always use underlying_container<void const*>, then const_cast when returning to the user?
My point was to allow ptr containers of <const T> to work, maintaining const-correctness. I believe that requires different underlying container types and not only one as you suggest. So in this code snippet: boost::ptr_vector<const int> v; v.push_back(new int); v[0] = 3; the assignment shall produce a compiler error as v[0] would be const, to maintain const-correctness. With the underlying type defined as mpl::if_<boost::is_const<T>, const void*, void*>::type this is accomplished. But using void* const always as the underlying type and using const_cast during returning (and inserting) elements, would not const-correctness be lost? Gerardo. 2010/10/15 Scott McMurray <me22.ca+boost@gmail.com>:
2010/10/14 Gerardo Hernández <g.hernandez@indizen.com>:
The problem is that the underlying type of boost::ptr_vector<T> is always vector<void*>, no matter T is const.
Since the point of this is to only ever instantiate one version of the underlying container, wouldn't it be better to always use underlying_container<void const*>, then const_cast when returning to the user?
Since we know we had a pointer to non-const at some point, the const_casts would all be legal, afaik. (const_cast atop an underlying_container<void*> would not be.)
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