Re: [Boost-users] [mpl::map & mpl::transform] Problems using mpl::map in mpl::for_each

From: David Abrahams (dave_at_[hidden])
Date: 2006-11-02 16:05:00

"Ovanes Markarian" <om_boost_at_[hidden]> writes:

> Hello,
>
> I have some slightly different code, which is presented in C++ Template Metaprogramming book to
> use the mpl::for_each function:
>
>
> mpl::for_each< mpl::transform<seq, wrap<_1> >::type >(dispatcher_type());

   mpl::for_each<seq, wrap<_> >(dispatcher_type());

would be simpler

> The deviation from the book is that my seq it not mpl::vector<...>, but mpl::map<...>
>
> In the docs is written, that mpl::transform operates on Forward Sequence. In the doc of forward
> sequence is stated that mpl::map is a model of it.

The last release of mpl::map had some considerable bugs.  Have you
tried the latest version from the CVS HEAD (or RC_1_34_0)?

> Unfortunately this code does not compile. I could transform the map
> to vector, but I would not like doing it, since that would cost
> compile time and slow down the compilation. Is it a known issue or
> should not I expect map to work with transform?

The code could "not compile" for many other reasons than that "map
doesn't work with transform."  Have you tried to compile

        typedef mpl::transform<seq, wrap<_1> >::type x;

> I also tried using itertors on seq, but that did not help.

I think we'll need a lot more detail to be able to help you.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com