Re: Using std::set::erase with iterators

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Mon, 3 Mar 2008 05:58:15 -0800 (PST)

Message-ID:

<ac7b6e3e-cf58-4892-8dd5-4b1497326c7c@d21g2000prf.googlegroups.com>

On Mar 3, 10:43 am, mathieu <mathieu.malate...@gmail.com> wrote:

  I do not understand how I am supposed to use erase when looping over
elements in a set, here is what I am trying to do (*). Could someone
please indicate how was I supposed to do it properly ? All I can think
of is something like this (very cumbersome):

    if( *it % 2 )
      {
      std::set<int>::const_iterator duplicate = it;
      ++it;
      s.erase( duplicate );
      }
    else
      {
      ++it;
      }

That's more or less the solution. You can simplify it a little:

    if ( *it % 2 ) {
        s.erase( it ++ ) ;
    } else {
        ++ it ;
    }

but that's about it. In the next version of the standard
(unless I misread something), you will be able to use the same
algorithm you'd use for the other containers:

    if ( *it % 2 != 0 ) {
        it = s.erase( it ) ;
    } else {
        ++ it ;
    }

Some implementations may support this already.

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James Kanze (GABI Software) email:james.kanze@gmail.com
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