[boost] Re: cref(_1)

From: David Abrahams (dave_at_[hidden])
Date: 2004-03-13 07:10:45

John Torjo <john.lists_at_[hidden]> writes:

>>It seems to me that, since I know that binding to an rvalue is
>>required, we ought to have a way to say "force this to be a const
>>ref".  I thought of something like
>>
>>        std::for_each(
>>            make_difference_iterator(p->second.begin())
>>          , make_difference_iterator(p->second.end())
>>          , boost::bind(&fu::writeVInt, &prox, boost::cref(_1)));
>>  
>>
>
> How about constifying the original sequence?

That wouldn't help.

> Something like:
>
>         std::for_each(
>             make_difference_iterator( constify( p->second.begin()))
>           , make_difference_iterator( constify( p->second.end()))
>           , boost::bind(&fu::writeVInt, &prox, boost::cref(_1)));
>
>
> Of course, constify it's just too easy to implement:
>
> template<class T> const T& constify(T &val) { return val; }

The problem is that dereferencing a difference_iterator yields an
rvalue.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com