Re: [Boost-users] Type List Iteration?

From: David Abrahams (dave_at_[hidden])
Date: 2005-10-05 08:50:54

Aleksey Gurtovoy <agurtovoy_at_[hidden]> writes:

>> I think you can see why I'd like a type list iterator solution to this. 
>
> Try this:
>
>     struct do_something
>     {
>         do_something( BASE* base ) : m_base( base ) {}
>
>         template< typename T > void operator()( mpl::identity<T> ) const
>         {
>             if ( T* x = dynamic_cast< T* >( this->m_base ) )
>                 some_function( x );
>         }
>
>         BASE* m_base;
>     };
>
>     mpl::for_each< 
>           mpl::vector<A,B,C>
>         , mpl::make_identity<_1>
>         >( do_something( base ) );
>

In this case you test for all the derived types, even if you match the
first one, so it's not identical.  It would probably be nice of us to
create a for_each_if() or until() function that stops when the
function object returns true.  I'm pretty sure I've needed something
like that before... Oh yeah, the FSM example could probably benefit
from it! A lot!

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