Re: Deleting items from std::list

From:
"P.J. Plauger" <pjp@dinkumware.com>
Newsgroups:
comp.lang.c++
Date:
Mon, 26 Jun 2006 09:45:11 -0400
Message-ID:
<C8ydnSktAqh6eQLZnZ2dnUVZ_sGdnZ2d@giganews.com>
"Howard Hinnant" <howard.hinnant@gmail.com> wrote in message
news:howard.hinnant-995E8D.08102226062006@syrcnyrdrs-01-ge0.nyroc.rr.com...

In article <1151276851.123572.175280@m73g2000cwd.googlegroups.com>,
"Markus Svilans" <msvilans@gmail.com> wrote:

std::list<int> data;

// [ code here to load data with values ]

std::list<int>::reverse_iterator ri = data.rbegin();

while (ri != data.rend())
{
    // Get next iterator in case ri is erased.
    std::list<int>::reverse_iterator next = ri;
    ++next;

    // Check if ri needs to be erased
    if (*ri == VALUE_TO_ERASE)
    {
        // [ code here to process *ri before erasing ]
        data.erase(ri); // <-- Causes compiler error
    }

    ri = next;
}

Obviously an erase method is not defined for reverse iterators in
std::list.

Is there a nice solution to this problem? Do I need to get a more
recent version of STLport?


for (std::list<int>::iterator ri = data.end(); ri != data.begin();)
{
   if (*--ri == VALUE_TO_ERASE)
   {
       // [ code here to process *ri before erasing ]
       ri = data.erase(ri);
   }
}


In case it gets lost in all the discussion of complexity, this is
the proper solution. Don't try to use reverse_iterators where
they're inappropriate -- just solve the problem.

P.J. Plauger
Dinkumware, Ltd.
http://www.dinkumware.com

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