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Recursive type synonyms



In view of the recent suggestion of Philip Wadler re: Recursive type synonyms

>The suggestion is:
>
>	Remove the restriction that type synonym
>	declarations must not be recursive.
>
>In other words, one could write things like
>
>	type  Stream a  =  (a, Stream a)
>
>which is equivalent to the type (a, (a, (a, ...))).

I think this is a very sensible proposal.  Furthermore, I believe that
implementing it would involve some exciting theory, viz. Peter Aczel's
Hyperset Theory (also known as ZFC-/AFA).

I strongly suggest Chapter 3 of the following book in this regard:

	THE LIAR: AN ESSAY ON TRUTH AND CIRCULARITY
	Jon Barwise and John Etchemendy
	Oxford University Press (1987).
	ISBN 0-19-505944-1 (PBK)
	Library of Congress BC199.P2B37

Varol Akman
Department of Computer Engineering and Information Science
Bilkent University, Bilkent, Ankara 06533, Turkey
Phone: +90 (4) 266-4133   Fax: +90 (4) 266-4126 or -4127
** Effective 1/1/1994, dial (312) instead of (4) above **
email:	akman@troy.cs.bilkent.edu.tr (preferred)
	akman@trbilun.bitnet