Re: [boost] Problem with range (make_iterator_range)?

From: Neal Becker (ndbecker2_at_[hidden])
Date: 2006-05-30 14:25:22

Thorsten Ottosen wrote:

> Neal Becker wrote:
>> Thorsten Ottosen wrote:
>> 
>> 
>>>Neal Becker wrote:
>>>
>>>>#include <boost/range.hpp>
>>>>#include <vector>
>>>>
>>>>template<typename in_t, typename out_t>
>>>>void copy (in_t const& in, out_t &out) {}
>>>
>>>What makes you think you can bind a temporary to
>>>an non-const reference (out)?
>>>
>> 
>> 
>> Yeah, same old problem.  I think the c+ standard should be changed.
> 
> Well, && will help some.
> 
>>  It's
>> quite clear (to me) that this is an important use of the range concept.
> 
> I think the algorothm is wrong in this case. I would go for
> 
> template< class SinglePassRange, class WritableForwardRange >
> void overwrite( const SinglePassRange&, WriteForwardRange& );
> 
> template< class SinglePassRange, class WritableForwardRange >
> void overwrite( const SinglePassRange&, const WriteForwardRange& );
> 

Did you mean something like this?
---------------------------
#include <boost/range.hpp>
#include <algorithm>
#include <vector>

template<typename in_t, typename out_t>
void copy (in_t const& in, out_t const& out) {
  std::copy (boost::begin (in), boost::end (in), boost::begin (out));
}

int main() {

  std::vector<int> out (2);

  copy (boost::sub_range<std::vector<int> > (out.begin(), out.begin()+2),
boost::sub_range<std::vector<int> > (out.begin(), out.begin()+2));
}
-----------------------------
Doesn't work, of course.  The call to '::copy' now matches but this doesn't
solve the basic problem:

g++ -o wrap.x86_64/test.os -c -g -DNDEBUG -DBOOST_DISABLE_THREADS -O3
-ftree-vectorize -ffast-math -fstrict-aliasing -Wall -fPIC -Isrc
-I/usr/local/src/boost.cvs -I/usr/include/python2.4 -Isrc-fixed -Isrc
wrap/test.cc
/usr/lib/gcc/x86_64-redhat-linux/4.1.1/../../../../include/c++/4.1.1/bits/stl_algobase.h:
In function '_OI std::__copy_aux(_II, _II, _OI) [with _II = const int*, _OI
= const int*]':
/usr/lib/gcc/x86_64-redhat-linux/4.1.1/../../../../include/c++/4.1.1/bits/stl_algobase.h:354:  
instantiated from 'static _OI std::__copy_normal<true, true>::copy_n(_II,
_II, _OI) [with _II = __gnu_cxx::__normal_iterator<const int*,
std::vector<int, std::allocator<int> > >, _OI =
__gnu_cxx::__normal_iterator<const int*, std::vector<int,
std::allocator<int> > >]'
/usr/lib/gcc/x86_64-redhat-linux/4.1.1/../../../../include/c++/4.1.1/bits/stl_algobase.h:387:  
instantiated from '_OutputIterator std::copy(_InputIterator,
_InputIterator, _OutputIterator) [with _InputIterator =
__gnu_cxx::__normal_iterator<const int*, std::vector<int,
std::allocator<int> > >, _OutputIterator =
__gnu_cxx::__normal_iterator<const int*, std::vector<int,
std::allocator<int> > >]'
wrap/test.cc:12:   instantiated from 'void copy(const in_t&, const out_t&)
[with in_t = boost::sub_range<std::vector<int, std::allocator<int> > >,
out_t = boost::sub_range<std::vector<int, std::allocator<int> > >]'
wrap/test.cc:20:   instantiated from here
/usr/lib/gcc/x86_64-redhat-linux/4.1.1/../../../../include/c++/4.1.1/bits/stl_algobase.h:317:
error: no matching function for call to 'std::__copy<true,
std::random_access_iterator_tag>::copy(const int*&, const int*&, const
int*&)'