Container insertion and removal

[Steven Schveighoffer]

On Mon, 08 Mar 2010 12:53:40 -0500, Andrei Alexandrescu  
<SeeWebsiteForEmail at erdani.org> wrote:

> Steven Schveighoffer wrote:
>> On Sun, 07 Mar 2010 12:43:09 -0500, Robert Jacques <sandford at jhu.edu>  
>> wrote:
>>
>>> On Sun, 07 Mar 2010 08:23:03 -0500, Steven Schveighoffer  
>>> <schveiguy at yahoo.com> wrote:
>>>> What is the advantage?  Why would an algorithm require soft  
>>>> functions?  What is an example of such an algorithm?
>>>
>>> Something that uses toUpperCase or toLowerCase, for example.
>>  I guess I won't get a real example.  I'm not sure it matters.  When  
>> Andrei starts implementing the soft methods, either they will be a huge  
>> win or obviously useless.  If I were a betting man, I'd bet on the  
>> latter, but I'm not really good at betting, and Andrei's ideas are  
>> usually good :)
>
> The way people usually take advantage of non-invalidating container  
> primitives is altering the container during an iteration. The canonical  
> way to remove while iterating an erase-non-invalidating container (e.g.  
> map) is this:
>
> typedef ... Container;
> Container c;
> for (Container::iterator i = c.begin(); i != c.end(); )
> {
>      if (should_delete_this_guy)
>          c.remove(i++);
>      else
>          ++i;
> }
>
> The canonical way to remove while iterating an erase-invalidating  
> container (e.g. vector) is:
>
> typedef ... Container;
> Container c;
> for (Container::iterator i = c.begin(); i != c.end(); )
> {
>      if (should_delete_this_guy)
>          i = c.remove(i);
>      else
>          ++i;
> }

Hm... this seems to be a different problem than I originally was thinking  
about.  So in essence, you want a set of "safe" functions that will not  
adversely affect a range you are using to iterate with?

BTW, I solved this problem (removing while iterating) in a much  
better/simpler way in dcollections.

-Steve