Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!sun-barr!sun!regenmeister!chrisp
From: chrisp@regenmeister.uucp (Chris Prael)
Newsgroups: comp.lang.misc
Subject: Re: Expressive Power - What is it ?
Message-ID: <33821@regenmeister.uucp>
Date: 31 May 89 18:15:17 GMT
References: <494@skye.ed.ac.uk>
Organization: Sun Microsystems, Inc. - Mtn View, CA
Lines: 19

From article <494@skye.ed.ac.uk>, by ken@aiai.ed.ac.uk (Ken Johnson):
> In article <769@cf-cm.UUCP> ted@computing-maths.cardiff.ac.uk (Ted Lawson) writes:
>> ... If, for every
>>	type, A's type includes B's corresponding type, then A
>>	is more expressive than B (or equally expressive)."
> 
> No, this doesn't seem to hold water as a complete definition.  Suppose
> that in language A I can form statements of the type S1, S2 and S3.  In

You might want to reread the statement.  Your example falls outside
Backus's statement.  A simplified restatement would be:

	If the set of all possible functions written in the language B is
	a subset of the set of all possible functions written in
	language A, then language A is more expressive than B.

Unfortunately, it is not a practically useful definition.

Chris Prael