Re: [stack] Why is point-free form so interesting?

----- Original Message ----- 
From: "William Tanksley, Jr" <[email protected]>
To: <[email protected]>
Sent: Wednesday, July 18, 2007 9:45 AM
Subject: Re: [stack] Why is point-free form so interesting?


> stevan apter <[email protected]> wrote:
> > William Tanksley, Jr wrote:
> > > None of them have multisets, which I'm starting to think may be
> > > semantically important for true out-of-order dataflow. It's fine to
> > > imagine that an array iteration is order-independent, but arrays are
> > > actually ordered.
> > i'm not following this.
> > a list has an order but you can ignore it.
> 
> Yes, but iteration over a list is ordered. That's the sort of minor
> distinction that can wind up making a difference in a heavy
> computation; especially since we're talking about a notation that's
> supposed to clearly express the idea of unordered dataflows.

so then use association arrays or the equivalent, which cannot
be accessed by position, only by name or the equivalent.  (of
course any implementation will order the symbol-value pairs in
some way, but who cares?)

> 
> Perhaps I could define implicit iteration to be unordered; thus,
> although the programmer is free (indeed, is required) to order arrays,
> the runtime won't promise anything about how the arrays get unpacked
> automatically.
> 
> There's a lot of possible implementations.
> 
> Of course, I'm not sure if my idea is a solution _at all_, so I'm a
> little leery of getting too much into the details.

i've been wondering whether, instead of having 'set' and 'multiset'
datatypes, you have two types of characteristic function.  a set cf
is a function f s.t. f x -> 1 iff x is in the set represented by
f, and f x -> n iff x occurs in the multiset n times.  then implement
set-algebra with h.o.f.'s 'union', 'diff', etc.  manfred?

> 
> -Billy
>