🚀 go-pugleaf

On 1 Nov 90 20:48:43 GMT, Chris.Holt@newcastle.ac.uk (Chris Holt) said:

Holt> Given an arbitrary domain, e.g. sets of integers, it is always
Holt> possible to introduce a monadic operation f that extends that
Holt> domain.  So, given a value such as {1,3,4}, we can apply f to
Holt> it to obtain a new value f{1,3,4}; and [ ... so on ... ]

Holt> The question is, why bother?  Forget about machine addresses and
Holt> locations and pointers right now;

Ah, but they are of the essence!  Machines actually work like that and
moving around elements of the codomain of f may be cheaper than moving
around elements of its domain. You can also, given the fact that you
have for other reasons to deal with f and its codomain, encode
information in the codomain (hash linking, BIBOP style tagging, ...).

Holt> the point is that introducing such an additional operation
Holt> complicates the domain, and I can't see any redeeming social value
Holt> in so doing (at least that has been presented yet).  But then, I
Holt> prefer programs to be as simple as possible...

It does complicate things (my original remark, please :->), but the
redeeming social value is that it may be more cost effective, *at the
appropriate (low) abstraction level*. That's a social, rather than
mathematical value:

Holt> This whole discussion of pointers (REFs) seems too concerned with
Holt> the wrong things to me (but then, I'm more concerned with
Holt> semantics; people worried about efficiency can hit "n" now).

I do agree that pointers are never necessary, and actually complicate
life, but they allow you to conserve space and time. Machine level
efficiency does matter, or else we would be using relational database
languages to write operating systems (not such a far fetched idea,
actually -- I have considered it...).

A lower constant factor of time or space complexity (because pointers do
not buy you more) is not interesting to the mathematician, but it is to
people that sign cheques.  I think that they are concerned with the
right things too.

As to me, I am concerned about both efficiency and semantics, and which
compromises between the two are feasible and cost effective under which
conditions.
--
Piercarlo "Peter" Grandi           | ARPA: pcg%uk.ac.aber.cs@nsfnet-relay.ac.uk
Dept of CS, UCW Aberystwyth        | UUCP: ...!mcsun!ukc!aber-cs!pcg
Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg@cs.aber.ac.uk