[Boost-users] Re: HowTo Iterator Facade

From: David Abrahams (dave_at_[hidden])
Date: 2004-12-05 07:34:38

David Abrahams wrote:
> Peter Dimov wrote:
> 
>> David Abrahams wrote:
>>
>>> Duane Murphy wrote:
>>>
>>>> I am implementing an iterator via iterator facade. The container
>>>> that the iterator is being used with can only return dereferenced
>>>> values by value (not by reference).
>>>>
>>>> If I implement the dereference() function (for facade) by returning a
>>>> value (instead of reference) then it appears that the iterator works
>>>> properly.
>>>> The most important operation that does _not_ work is that the
>>>> iterator cannot be used with bind(). (bind cannot be used with 
>>>> non-const
>>>> return types.) 
>>>
>>>
>>>
>>> Sorry, I can't imagine what you mean.  Of course bind works with
>>> non-const return types: [...]
>>
>>
>>
>> Probably the following:
>>
>>    std::for_each( first, last, boost::bind( f, _1 ) );
>>
>> When *first returns a non-const rvalue, bind can't take it.
> 
> 
> I guess the answer is to make the reference type const, then.

That will suppress the iterator's writability, though.  I hope it's desired.

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com