Re: [boost] [iterator] Constness of counting_iterator

Subject: Re: [boost] [iterator] Constness of counting_iterator
From: Dave Abrahams (dave_at_[hidden])
Date: 2013-02-01 12:06:58

on Fri Feb 01 2013, Claas <claas.koehler-AT-dlr.de> wrote:

> Hi all!
>
> I was wondering why the dereference operator of counting_iterator<T> returns a constant reference to
> T instead of a reference to T.
>
> Naively I would expect counting_iterator<T>::reference to be T& and counting_iterator<const
> T>::reference to be const T&.
>
> I suppose however that there was good reason to implement counting_iterator the way it is
> implemented. Could anyone kindly point this reason out to me?

Counting iterators are strictly constant iterators.  Writing into a
counting iterator would alter its position in the sequence.  That
doesn't seem compatible with the expected behavior of iterators that
could be used by any algorithm.

-- 
Dave Abrahams
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