[boost] [Property Map] Composition of properties

From: Benoit (benoit.casoetto_at_[hidden])
Date: 2006-09-15 02:35:24

Hello everyone,

I have been using properties quite extensively in my work.
And these last days i have needed to combine properties numerous times.

By that, i mean that i have n properties p1, p2, ... pn and what i use is
      get( p1, get( p2, get( ..., get( pn, object )  ... ) ) )
I would very much want to make a composite property p to be used like this :
      get( p, object )
(most of the time, n=2, but why stop there ? :-) )

I have to tried to find such functionality but in vain so far... Does
it not exist ? Are there obstacles that i have not foreseen ? I am
thinking of something like the following :

        template<class Prop1, class Prop2>
        struct composite_property
        {
                composite_property( Prop1 p1_, Prop2 p2_ ) :
                        p1( p1_ ), p2( p2_ )
                {
                }

                Prop1 p1;
                Prop2 p2;
        };

        template<class Prop1, class Prop2>
        typename property_traits<Prop1>::reference
                get(composite_property<Prop1, Prop2> comp,
                        typename property_traits<Prop2>::reference x )
        {
                return get( comp.p1, get( comp.p2, x ) );
        }

How do you all feel about this ? I believe it would be very useful !

-- 
Benoît Casoetto