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

On Fri, 13 Jul 2007, Christopher Diggins wrote:

> On 7/10/07, William Tanksley, Jr <[email protected]> wrote:
>> John Carter <[email protected]> wrote:
>>> Christopher Diggins 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)
>>> * Trivial (Adds almost nothing to the code / vanishes in
>>> this representation)?
>> >snip<
>> Stack notation is NOT the simplest possible data transfer notation; it
>> imposes a total ordering on data, when often a partial ordering is
>> sufficient.
>
> This is an interesting point. Specifying an ordering where non is
> intended.
  >snip<
> Many programming languages don't even bother allowing people to
> specify unordered data because it would introduce new constructs,
> operations, or representations into their language, thus increasing
> complexity.


Aha! Here we have the meat of it.

Yes, having an unorder data type is implementationwise more complex,
but semantically simpler.

I suspect "unordered set" needs to be a (or the) primitive.

Arrays and lists are a premature optimization that make reasoning
about the langauge harder as they add spurious information that has to
be dealt with.

Parameters probably should be a set, and a binding should be a map (an
unordered set of pairs).

John Carter                             Phone : (64)(3) 358 6639
Tait Electronics                        Fax   : (64)(3) 359 4632
PO Box 1645 Christchurch                Email : [email protected]
New Zealand