Re: Re: TypeLISP

From: Vladimir Prus (ghost_at_[hidden])
Date: 2000-12-01 07:56:47

> On Thu, 30 Nov 2000 netterdag_at_[hidden] wrote:

> > Recently I made a *very* experimental typelist implementation
> > with some "LISP"-like functionality. 

Jeremy Siek <jsiek_at_[hidden]> wrote:
 
> Just want to note that a cons-list is conceptually similar to the tuple
> of the LL, ....

1. It seems to me that there's great difference between tuple and type-list.
The former is runtime object, while the latter is compile-time list, made up of
template specializations. Or am I mistaken about LL tuples?

2. I once tried to make type-lists myself and have found that:
        -	once created, they can be used at compile time in virtually any
                way
        -	Wholesale creation of a list is possible but ugly.
        -	Appending anything to the list is very problematic. You need to
                specialize the last element, and you have to know what that
                element is.  Finding the element by traversing the list won't
                do, because you'll  use default specialization of the last element. 
                So you have either provide the last element manually or use very 
                 fragile methods.

3. While type-list could be very good for language extensions (I tried 
storing list of concepts implemented by a class in them for the purpose of
concept-based overloading), convenient usage of 'em is a problem. I'm not sure
if it's possible.

Regards,	
Vladimir