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From: Ian Collins <ian-news@hotmail.com>
Newsgroups: comp.lang.c++
Subject: Re: Defining iterator type through container object type
Date: Thu, 15 Sep 2011 10:25:31 +1200
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On 09/15/11 09:51 AM, Urs Thuermann wrote:
> Can I define an iterator for an object of a standard container class
> without using the concrete type of that container object?
>
> I tried things like
>
>      1 #include<list>
>      2 void foo(std::list<int>  ilist) {
>      3     ilist.iterator it;
>      4     for (it = ilist.begin(); it != ilist.end(); ++it) { *it; }
>      5 }
>
> and
>
>      1 #include<list>
>      2 void foo(std::list<int>  ilist) {
>      3     typeof(ilist)::iterator it;
>      4     for (it = ilist.begin(); it != ilist.end(); ++it) { *it; }
>      5 }
>
> For the first code I get
>
>      foo.cc:3:11: error: invalid use of 'std::list<int>::iterator'
>
> so at least ilist.iterator seems indeed to be understood as
> std::list<int>::iterator.  In the second case I get
>
>      foo.cc:3:29: error: expected initializer before 'it'
>
> Is there a way to define the iterator without using std::list<int>::iterator
> explicitly?

Only if your compiler supports the new auto keyword.  Otherwise use a 
typedef for the parameter type.

-- 
Ian Collins