Re: C++ standard and current implementation

From:

desktop <fff@sss.com>

Newsgroups:

comp.lang.c++

Date:

Mon, 11 Jun 2007 10:14:26 +0200

Message-ID:

<f4j08v$fhs$1@news.net.uni-c.dk>

Alan Johnson wrote:

desktop wrote:

I the C++ standard page 472 it says that an associative container can
be constructed like X(i,j,c) where i and j are input iterators to
elements. But in the implementation there is no constructor that
matches this requirement, the only constructors are:

public:
      // allocation/deallocation
      _Rb_tree()
      { }

      _Rb_tree(const _Compare& __comp)
      : _M_impl(allocator_type(), __comp)
      { }

      _Rb_tree(const _Compare& __comp, const allocator_type& __a)
      : _M_impl(__a, __comp)
      { }

      _Rb_tree(const _Rb_tree<_Key, _Val, _KeyOfValue, _Compare,
_Alloc>& __x)
      : _M_impl(__x.get_allocator(), __x._M_impl._M_key_compare)
      {
    if (__x._M_root() != 0)
      {
        _M_root() = _M_copy(__x._M_begin(), _M_end());
        _M_leftmost() = _S_minimum(_M_root());
        _M_rightmost() = _S_maximum(_M_root());
        _M_impl._M_node_count = __x._M_impl._M_node_count;
      }
      }

      ~_Rb_tree()
      { _M_erase(_M_begin()); }

How does the implementation meet this requirement when the constructor
is not implemented?

Nowhere in any part of the standard does it mention the class _Rb_tree,
much less that it satisfies the requirements for an associative container.

_Rb_tree is at most an implementation detail of your specific
implementation. There isn't much of a compelling reason to be digging
around through it unless you are observing some specific incorrect
behavior in your implementation.

But how is it out of curiosity that the following works:

    std::vector<int> hh;
    hh.push_back(1);
    hh.push_back(2);
    hh.push_back(3);
    std::vector<int>::iterator it1 = hh.begin();
    std::vector<int>::iterator it2 = hh.end();
    std::set<int> my_set(it1,it2);

when there is no matching constructor for (it1,it2) in the above
implementation on my system.