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From: mark@parc.xerox.com (Mark Weiser)
Newsgroups: comp.theory
Subject: Re: Procedures with multiple out parameters: why not?
Message-ID: <516@roo.UUCP>
Date: 17 Aug 90 04:29:31 GMT
References: <1990Aug15.231838.5664@zaphod.mps.ohio-state.edu> <21458@grebyn.com>
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Perhaps it depends on what counts as more than one out parameter.

Many languages permit the return of record structures, and the selection
of components as part of the call.  This could be argued as a form of
multiple out parameters.  (e.g.:
	PROC foo [] RETURNS RECORD [i,j: INT];
	...
	x = foo[].i;

If the issue is something like value vs. var parameters, then the restriction
could be restated as saying that it is bad to have ANY out parameters (i.e.
any var parameters)--only return of a (possibly complex value) should be
permitted.  This seems to be in agreement with formal practice also.  I would
guess it is in line with Dijkstra's intent.

-mark
--
Spoken: Mark Weiser 	ARPA:	weiser@xerox.com	Phone: +1-415-494-4406