Re: [boost] De Bruijn Bind (alternate bind syntax) Interest?

Subject: Re: [boost] De Bruijn Bind (alternate bind syntax) Interest?
From: Larry Evans (cppljevans_at_[hidden])
Date: 2010-09-20 14:02:26

On 09/20/10 10:43, David Sankel wrote:
[snip]
> 
> The z function in the example is a weird beast. I gave it a trivial
> implementation:
> 
>     struct Z2
>     {
>         typedef int result_type;
>         template < typename F, typename G >
>         int operator()( F f
>                       , G g
>                       ) const
>         {
>             return 3;
>         };
> 
>     } const z2 = Z2();
> 
> To make a non-trivial implementation of z, you could use the fact that its
> first argument has kind * → *. That is, its first argument must be a
> function from something to something. Its second argument has kind ((* → *)
> → *) → *). That is, its second argument must be a function that takes in a
> function as its first parameter that  takes in a function as its first
> parameter. A fun mind bender :).
> 
> David
> 
Thanks David.

On reason I got interested in wiki is because I was having problems
doing it for types instead of values.  This type de_bruijn code
is here:

  http://svn.boost.org/svn/boost/sandbox/variadic_templates/libs
    /mpl/sandbox/de_bruijn/eval.cpp

As indicated by the Status: comment, I'm having some problems.
I just thought I'd upload it in case anyone else has some
idea where I'm going wrong.  I'll look at your code, with
the modifications you suggest above, to see if that'll
give me some ideas.  BTW, the context in your value de_bruijn
looks like the args in my type de_bruijn.  IOW, it keeps track
of the current args and the depth in the expression tree.
I have yet figured out what any further comparision between
the value and type de_bruijn are, but I'd be curious.

-regards,
Larry