Path: utzoo!attcan!uunet!fernwood!decwrl!elroy.jpl.nasa.gov!usc!zaphod.mps.ohio-state.edu!think!snorkelwacker!bloom-beacon!eru!luth!sunic!mcsun!ukc!dcl-cs!aber-cs!pcg
From: pcg@aber-cs.UUCP (Piercarlo Grandi)
Newsgroups: comp.arch
Subject: Re: Paper tape vs card structuring
Message-ID: <1656@aber-cs.UUCP>
Date: 22 Feb 90 02:33:59 GMT
Reply-To: pcg@cs.aber.ac.uk (Piercarlo Grandi)
Organization: Dept of CS, UCW Aberystwyth
	(Disclaimer: my statements are purely personal)
Lines: 35

In article <983@m1.cs.man.ac.uk> mshute@r4.UUCP (Malcolm Shute) writes:
  In article <1639@aber-cs.UUCP> pcg@cs.aber.ac.uk (Piercarlo Grandi) writes:
  
  >[...] the difference between encoded (paper tape) and structural
  >(card deck) representations of data. In encoded representations the
  >relationships among parts of composite data are encoded within the data, in
  >structural representations they are part of the data structure; [...]
  >I know of languages that are mostly structural (Lisp) [...]
  >[...] most architectures are structural (machine programs are represented as
  >graphs), but some could be argued to be encoded (e.g. reduction machines).
  
  But machines which employ String Reduction are generally executing
  something which looks like low level Lisp, so by your definition will
  be 'card-deck' machines; and machines which employ Graph Reduction must
  surely fit also into your 'structured representation' category.
  So I am unclear about your definitions here... can you elaborate.

In a fuzzy way -- I covered may back in the other article saying that very
few examples are "pure".

I think that things like the SK combinator reduction systems (with which
I am not very familiar -- had a look at them many years ago) are really
processing a string using a parser. They don't really navigate the
program. The use of combinators means that the structural relationships
among parts of the program are encoded in the program, not out-of-band.

Frankly I am hard pressed to think of an architecture that is really
encoded. Computers are not good at dealing with encoded information, humans
are. That's why parsing and prettyprinting phases exist, after all (the
other reason is that computers deal with electric and magnetic "charges",
humans with "wawes").
-- 
Piercarlo "Peter" Grandi           | ARPA: pcg%cs.aber.ac.uk@nsfnet-relay.ac.uk
Dept of CS, UCW Aberystwyth        | UUCP: ...!mcvax!ukc!aber-cs!pcg
Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg@cs.aber.ac.uk