Re: [boost] Re: typelists: MPL tutorial + partial review

From: Peter Dimov (pdimov_at_[hidden])
Date: 2001-12-12 13:41:03

From: "Mat Marcus" <mmarcus_at_[hidden]>
> By the way I'm not knocking Loki. I think Loki is cool. As I mentioned
> above, I don't want to wait two years until we move to an adequate
> compiler; I want to use it today. I am just trying to focus our Loki,
> MPL discussion.
>
>      Mark>   You work shows that it is possible to maintain a nice
>      Mark> recursion interface while still achieving working code on
>      Mark> such platforms.
>
> Thanks. But I'm not sure I understand what you mean by a recursion
> interface? The interface to the hierarchy generators is more or less
> unchanged. Do you mean recursive implementation.  Well that is there
> too under the hood.  It seems convenient to have some higher level
> abstractions so that I don't have to repeat the pattern matching code
> endlessly. While the applicitave for_each style may take some learning
> I believe that it is a useful way to factor out common code, just as
> stl::for_each offers a way to visit each element in a sequence.

I can't help but think that the discussion is somehow missing the point.

The novel paradigm presented by MPL is indeed very interesting, but there is
no reason for this paradigm to "compete" with the old-school Lisp approach.
It must be implemented on top of it. Just like the STL for_each is
implemented on top of the old C-style for loop, and the STL does not
_prevent_ me from using a for loop if I so desire.

As a starting point, we simply need to define the standard A.B data
structure of compile-time C++. Anything else can be implemented on top of
it. I don't see why the existence of MPL should change that.

--
Peter Dimov
Multi Media Ltd.