Re: [Boost-users] iterator_facade and distance()

Subject: Re: [Boost-users] iterator_facade and distance()
From: Dave Abrahams (dave_at_[hidden])
Date: 2011-04-16 00:12:53

At Sat, 16 Apr 2011 09:55:31 +0900,
Andrej van der Zee wrote:
> 
> Hi,
> 
> I am trying to implement an iterator using boost::iterator_facade. It
> works fine but it is very slow, I think because the distance()
> function takes lineair time as it is seems to be implemented in terms
> of increment(). I would like to implement the distance() function
> myself but I am not sure how. I tried to implement distance_to() like
> this:
> 
>  class const_data_stream_iterator :
>     public boost::iterator_facade<const_data_stream_iterator,
>     char const,
>     boost::forward_traversal_tag>
>   {
>     public:
> 
>       typedef boost::iterator_facade<const_data_stream_iterator, char
> const, boost::forward_traversal_tag> facade_t;
> 
>     private:
> 
>       friend class boost::iterator_core_access;
> 
>       facade_t::difference_type
> difference_to(const_data_stream_iterator & to) const
>       {
>         ...
>       }
>  };
> 
> But this does not work. How can I do this?

You misspelled "distance_to."  Fix the spelling and it should work better.

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com