Re: member iterator - request for comment

From:

Nick Hounsome <nick.hounsome@gmail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Tue, 22 Jun 2010 17:28:36 CST

Message-ID:

<5d9f22ab-4417-4eca-a419-fc32766d255b@d37g2000yqm.googlegroups.com>

On 21 June, 14:06, Mikosz <mikosz...@gmail.com> wrote:

Hi,

Recently I've met the need to perform operations like this quite
often:

struct A {
int val;

}

...
std::vector<A> as;
...
std::set<int> vals;
std::vector<A>::const_iterator it, end = as.end();
for (it = as.begin(); it != end; ++it) {
vals.insert(it->val);

}

that is, to perform some action on one of the members of each of the
collection's elements. I couldn't find any solutions within the STL,
so I've created my own MemberIterator class. The code is:

My first thought was to make a decorator collection that presents a
(obviouly const) collection as a collection of some member.
It would work for your example but would otherwise be less flexible.

My second thought was to wonder whether you could just deduce the type
from the member pointer.

My third thought - and it should probably have been my first - is that
your result is far less readable than the original.
Maybe it's me but I find explicit loops to be more comprehensible in
90% of cases.

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