iter_swap on move_iterator

[François Dumont]

Hi

     While working on removal of code duplications in algos 
implementation I challenge them with move_iterator. I started with 
stable_sort and it doesn't compile. I summarize the problem to the fact 
that iter_swap can't be used on move_iterator. As, in C++11, iter_swap 
simply forward to swap(*__a, *__b) it is normal that it can't accept 
rvalue but shouldn't iter_swap be adapted to accept move_iterator ?

     I also find the compilation error message surprising. I have added 
a call to iter_swap in 24_iterators/move_iterator/greedy_ops.cc and the 
error message is:

In file included from 
/home/fdt/dev/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/bits/char_traits.h:41:0, 

                  from 
/home/fdt/dev/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/ios:41, 

                  from 
/home/fdt/dev/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/ostream:40, 

                  from 
/home/fdt/dev/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/iterator:64, 

                  from 
/home/fdt/dev/gcc/libstdc++-v3/testsuite/24_iterators/move_iterator/greedy_ops.cc:20: 

/home/fdt/dev/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/bits/stl_algobase.h: 
In instantiation of 'void std::iter_swap(_ForwardIterator1, 
_ForwardIterator2) [with _ForwardIterator1 = 
std::move_iterator<greedy_ops::X*>; _ForwardIterator2 = 
std::move_iterator<greedy_ops::X*>]':
/home/fdt/dev/gcc/libstdc++-v3/testsuite/24_iterators/move_iterator/greedy_ops.cc:39:24:   
required from here
/home/fdt/dev/gcc-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/bits/stl_algobase.h:148:7: 
error: no matching function for call to 
'swap(std::move_iterator<greedy_ops::X*>::value_type, 
std::move_iterator<greedy_ops::X*>::value_type)'
        swap(*__a, *__b);
        ^

Why is the comipiler talking about a call to swap on 
move_iterator<greedy_ops::X*>::value_type. It should be on the return 
type of move_iterator operator* which is move_iterator<>::reference, no ?

François