Re: copy from keys from multimap into the vector

From:

peter koch <peter.koch.larsen@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Wed, 29 Oct 2008 14:33:56 -0700 (PDT)

Message-ID:

<e04822dc-778d-4650-a3e1-f636f7626fc9@c60g2000hsf.googlegroups.com>

On 29 Okt., 22:25, "AnonMail2...@gmail.com" <AnonMail2...@gmail.com>
wrote:

I am using while loop for that but I am sure you can do it quicker an=

more syntactically clear with copy function.

Here is what I do and would like to if someone has a cleaner solution=

    vector<string> vec;
    multimap<stirng, int> myMap

   // populate myMap

    multimap<string, int >::iterator iter = myMap.begin();

    while(iter != myMap.end())
    {
           vec.push_back(iter->first)
    }

Whats wrong with
std::copy(myMap.begin(),myMap.end(),std::back_inserter(vec)); ?

A map's element contains both the key and the value so this is not
correct.
The OP just wants the key.

I did not see that. Don't ask the question in the title (but read the
title anyway!).
In that case, I'd recommend having a look at Boosts iterator adaptors
which should do the job. But I admit that I haven't looked at that
part of Boost for a while (and never used it).

/Peter