RE: [boost] Re: ICE ICE BABY! (my MPL code is ICEing)

From: Brian Braatz (brianb_at_[hidden])
Date: 2005-06-05 14:18:06

> >>
> >>template <class type_t, class sequence_t>
> >>struct copy_col_if_in_dest
> >>: public if_< typename is_same< typename deref<typename
> >>boost::mpl::find<sequence_t, type_t>::type >::type, type_t>,
> >
> > do_copy_col,
> >
> >>do_not_copy_col>::type
> >>{
> >>};
> 
> This code has a problem when type_t is not in sequence_t: the
> past-the-end iterator gets dereferenced. I wrote a short program to do
> what you want (it's more explicit, it uses mpl::contains<>):
> 
> #include <boost/mpl/vector.hpp>
> #include <boost/mpl/if.hpp>
> #include <boost/mpl/contains.hpp>
> 
> namespace mpl = boost::mpl;
> 
> struct do_copy_col {};
> struct dont_copy_col {};
> 
> template<typename T, typename Seq>
> struct copy_col_if_in_dest
>      : mpl::if_<
>            mpl::contains<Seq, T>,
>            do_copy_col,
>            dont_copy_col
>        >::type
> {
> };
> 
> int main()
> {
>      typedef mpl::vector<char, short, int, long> v;
>      do_copy_col do_copy = copy_col_if_in_dest<int, v>();
>      dont_copy_col dont_copy = copy_col_if_in_dest<bool, v>();
>      return 0;
> }
> 

[Brian Braatz Writes:] 
Wow. Many THANKS- the mpl::contains<> is REALLY what I was looking for.
(Though the exercise of doing it with if_<> was a useful experience)

THANK YOU 

( I have been burning the morning and afternoon oil here the last few
weeks trying to get a lib I am proposing ready for boost people to look
at)

-I am going to replace the code I had with the code you presented, and
make a note of your contribution.

THANKS AGAIN!

Brian