libstdc++/7186: DR179 for std::deque::iterator and const_iterator

[pcarlini@unitus.it]

>Number:         7186
>Category:       libstdc++
>Synopsis:       DR179 for std::deque::iterator and const_iterator
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jul 02 12:16:09 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     Paolo Carlini
>Release:        3.1 and current 3.1.1 and 3.2
>Organization:
>Environment:
don't care
>Description:
This is a follow up of libstdc++/6642, now fixed in the
mainline, concerning std::deque: the resolution of DR179
<Ready> needs to be implemented for operator- of
std::deque::iterator and std::deque::const_iterator too.
This is a testcase, which currently does not compile at all
whereas it should:
//////////
#include <deque>

int main()
{
  std::deque<int> d;
  std::deque<int>::iterator it = d.begin();
  std::deque<int>::const_iterator cit = d.begin();

  return it - cit;
}
//////////
>How-To-Repeat:

>Fix:
The tricky point is not affecting the behaviour of reverse
iterators about which the status of the relevant DR280
is still <open>.
>Release-Note:
>Audit-Trail:
>Unformatted: