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From: ted@computing-maths.cardiff.ac.uk (Ted Lawson)
Newsgroups: comp.lang.misc
Subject: Expressive Power - What is it ?
Message-ID: <769@cf-cm.UUCP>
Date: 28 May 89 11:47:06 GMT
Reply-To: ted@computing-maths.cardiff.ac.uk (Ted Lawson)
Organization: University of Wales College of Cardiff, Cardiff, WALES, UK.
Lines: 22


	Can anyone provide or (preferably) point-to a definition of,
	or discussion about, the oft-heard term "Expressive Power" ?

	All I can find is John Backus's '77 Turing Award Lecture
	where he says:

	"...language A would be more expressive than language B
	under the following roughly stated conditions. First,
	form all possible functions of all types in A by applying
	all existing functions to objects and to each other in all
	possible ways until no new function of any type can be
	formed. ... Do the same for language B. Next, compare each
	type in A to the corresponding type in B. If, for every
	type, A's type includes B's corresponding type, then A
	is more expressive than B (or equally expressive)."

				[Comm. ACM 21(8) 623-624, 1978].

	Is this the last word ?

	Ted Lawson