[boost] [proto] docs unclear (to me) for: "Expression Nodes as Fusion Sequences"

From: Markus Werle (numerical.simulation_at_[hidden])
Date: 2008-03-11 10:33:08

Hi!

In the section "Expression Nodes as Fusion Sequences"
you show the follwing code

struct fun_t {};
terminal<fun_t>::type const fun = {{}};

// ...
fusion::for_each(
    fusion::transform(
        // pop_front() removes the "fun" child
        fusion::pop_front(fun(1,2,3,4))
        // Extract the ints from the terminal nodes
      , functional::arg<>()
    )
  , display()
);

It did not became clear to me why a terminal<fun_t>::type 
can be initialized with 4 integer arguments.

I thought terminal<fun_t>::type is equivalent to 
expr< tag::terminal, args0< fun_t >, 0 >
and should take no args at all.
Could you clarify this? 

Markus