Re: [boost] problem with permuation_iterator (constness)

From: François Duranleau (duranlef_at_[hidden])
Date: 2006-11-06 10:22:26

On Mon, 6 Nov 2006, Neal Becker wrote:

> This simple test illustrates the problem:
>
> #include <boost/iterator/permutation_iterator.hpp>
> #include <vector>
> #include <boost/range.hpp>
>
> template<typename in_t>
> void F (in_t const& in) {
>  typename boost::range_const_iterator<in_t>::type inp = boost::begin (in);
> }
>
> int main () {
>  std::vector<int> x, y;
>  F (boost::make_permutation_iterator (boost::begin (x), boost::begin (y)));
> }
>
> /usr/local/src/boost.hg/boost/range/const_iterator.hpp:37: error: no type
> named
> const_iterator in class
> boost::permutation_iterator<__gnu_cxx::__normal_iterator<int*,
> std::vector<int, std::allocator<int> > >,
> __gnu_cxx::__normal_iterator<int*, std::vector<int, std::allocator<int> > >

The problem has nothing to do with constness. make_permutation_iterator 
return's an iterator (a permutation_iterator), not a range. But you try to 
use it as a range. To get the range, to need to call 
make_permutation_iterator twice: once as you did, and another time with 
'end'.

-- 
François Duranleau
LIGUM, Université de Montréal
"The real source of wealth is correct ideas: workable ideas: that is,
  negative entropy -- Information."
                           - Robert Anton Wilson, _Prometheus Rising_, 1983