Hi Doug and Johan:

In class yesterday, Larry Dodds questioned why we explictly send
several visitors along with a traversal. Why not one?

Since Demeter/Java allows now to declare classes explicitly as visitor
classes, we could adopt the following rule:

void f() to X (V);

is equivalent to

void f(x) to X (V,V1,V2, ... ,Vk) 

where V1 through Vk are all the visitor
classes reachable in depth-first order from V (in the class graph).

V could be a deeply nested visitor class. The only tricky issue is that
we have to order the part classes of V so that the depth-first order
will give the correct visitor ordering.

With the current language, composing visitors and ordering them
are separated. The above suggests to combine the two. I think that in many
situations, such a combination is convenient.

The visitor object would be constructed as a minimal object according
to the cd and  and then all the init 
methods would be applied.

What is your current view on the multiple visitor class problem?

-- Karl