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

On 7/13/07, William Tanksley, Jr <[email protected]> wrote:
> Christopher Diggins <[email protected]> wrote:
> > John Carter < [email protected]> wrote:
> > > Is there a representation of a program where the mechanism of moving
> > > parameters to values in expressions is...
> > > * Explicit (ie. Can be reasoned about / transparent on inlining)
>
> > I like this a lot. This does a good job of summing up what I like
> > about point-free form very elegantly. One point though, is "explicit"
> > the correct term? I would normally consider argument passing in a
> > stack-language to be implicit, rather than explicit. However I agree
> > that it is obvious and unambiguous.
>
> Actually, I think John made a mistake in another word: the mechanism
> for moving _values_ from source to consumption is explicit. You're not
> moving "parameters", nor are they being moved to "values". But yes,
> the mechanism is explicit.
>
> And also, yes, you're right that parameter passing is (in some sense) implicit.
>
> > - order of evaluation is simple and unambiguous: left to right (no
> > precedence rules)
> > - subterms can be evaluated concurrently
>
> Aren't these contradictory?

I'm simply doing a poor job of saying what I mean.

What I was trying to say is that composition is always left-right, but
that subterms could be evaluated separately and in any order. IOW:

t = a b c d
== ((a b) (c d))
== ((a b) c) d)

- Christopher