Re: [boost] Filter Iterator question

From: John Torjo (john.lists_at_[hidden])
Date: 2003-12-08 19:40:35

Robert Ramey wrote:

> I have a question regarding the filter_iterator which
> is illustrated by the following small program:
> 
> #include <list>
> #include <algorithm>
> #include <boost/config.hpp>
> #include <boost/compatibility/cpp_c_headers/cctype>
> #include <boost/iterator/filter_iterator.hpp>
> 
> struct remove_whitespace_predicate
> {
>     char operator()(char t){
>         return ! std::isspace(t);
>     }
> };
> 
> main(){
>     typedef boost::filter_iterator<
>         remove_whitespace_predicate,
>         std::list<char>::const_iterator
>     > fi;
> 
>     std::list<char> clist;
>     std::list<char> olist;
>     std::copy(
>         fi(clist.begin(), clist.end()),
>         fi(), // ? what goes here
>         std::back_inserter(olist)
>     );
> }
you could always use rtl ;)

Or,

     std::copy(
         fi(clist.begin(), clist.end()),
         fi( clist.end(), clist.end()), // ? what goes here
         std::back_inserter(olist)
     );

Best,
John

> 
> ? what goes here ?
> fi() doesn't work because base() != base(clist.end())
> fi(clist.end()) crashes because the constructor for
> fi dereferences its iterator argument which is not always
> possible when the iterator corresponds to one more than
> the end of the list.
> 
> Does anyone have something to recommend?
> 
> Robert Ramey
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