Re: Deleting items from std::list

From:

"P.J. Plauger" <pjp@dinkumware.com>

Newsgroups:

comp.lang.c++

Date:

Mon, 26 Jun 2006 19:50:48 -0400

Message-ID:

<NvqdnYB3A6BF7z3ZnZ2dnUVZ_tednZ2d@giganews.com>

"Markus Schoder" <a3vr6dsg-usenet@yahoo.de> wrote in message
news:44a02da0$0$29123$9b4e6d93@newsread4.arcor-online.net...

Howard Hinnant wrote:

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.

The solution below is better but just for completeness sake

data.erase(ri.base());

should work.

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);
    }
}

For completeness sake you have to specify how to make it past the
erased element with your reverse iterator. It's way messier than
for Hinnant's direct solution.

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