On Sun, Nov 14, 2010 at 13:06, viboes <vicente.botet@wanadoo.fr> wrote:
Dan Tsafrir wrote:
I believe this very issue was addressed and solved by the committee. Specifically, the allocator proposal (which got accepted to c++0x) was revised to include the following paragraph (see p. 5 of [2]):
"The key requirements for an allocator’s pointer type are that it has pointer-like syntax (i.e., it can be dereferenced using operator*), that it is implicitly convertible to the corresponding void_pointer and explicitly convertible from the corresponding void_pointer, and that there exists a specialization of the pointer_traits class template, which describes a number of key attributes of the pointer type. If an allocator does not define a pointer type, allocator_traits will provide default types for pointer, const_pointer, void_pointer, and const_void_pointer of value_type*, const value*, void*, and const void*, respectively. The above pointer requirements were carefully crafted to be harmonious with the intent of N2913 (SCARY Iterator Assignment and Initialization)."
The SCARY proposal was synchronously revised to allow the iterator to depend upon the types X::allocator_type::const_void_pointer and X::allocator_type::void_pointer (where X is a container) thereby ridding programmers from the need to depend on the allocator type (see [3]).
From what I read this should answer I question I posted in this thread. It seems that the C++0x proposal is taking in account this technique seriously. Does C++0x proposal requires SCARY implementations for containers?
SCARY generated quite a controversy because on the one hand it was backed by key figures but on the other hand it was proposed very late in the standardization process; specifically, the committee convener strongly objected to SCARY, arguing that dealing with this issue so late in the process is unacceptable (search for occurrences of "scary" in [1] to see the discussion). It was eventually decided to postpone SCARY to the next C++ revision (c++1y?), and the issue has been assigned with a "NAD Future" status (search for "scary" in [2]). Best, --Dan [1] "Minutes of WG21 Meeting, October 19, 2009", committee paper N3003 http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2009/n3003.pdf [2] "C++ Standard Library Issues List" http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-status.html