Re: container idiom revisited

From:
James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Wed, 14 Apr 2010 15:59:12 -0700 (PDT)
Message-ID:
<00d962cf-7b27-40ef-a63d-bf11f51b4649@u31g2000yqb.googlegroups.com>
On Apr 14, 12:37 am, keith <johndoe64...@yahoo.com> wrote:

It's a defect in the standard. See, e.g, issue 355 in:
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2004/n1685.html

Also: the bug has been fixed in the draft for C++0X.


I see. How then to erase the last element of a std::multimap<>?


    std::multimap<>::iterator i = m.end();
    -- i;
    m.erase(i);

It isn't too difficult (and is generally useful) to write a
generic pred() function which can be used.

I've tried mmap.erase(mmap.rbegin());, but it does not work.


Rather obviouslym since multimap<>::erase expects a
multimap<>::iterator.

mmap.erase(--mmap.end()), does work however.


On some (most? all?) implementations.

I don't see the construct being wrong for a
std::multimap<>::iterator (or any other associate iterator),
because they are not random but bidirectional. Consequently I
see them being of class type.


And? Class type doesn't guarantee that --mmap.end() will work.

--
James Kanze

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