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From: eerke@cs.kun.nl (Eerke Boiten)
Newsgroups: comp.theory
Subject: Re: Why not multiple out parameters? [again]
Message-ID: <2147@wn1.sci.kun.nl>
Date: 12 Sep 90 09:10:37 GMT
References: <1990Aug28.203643.11214@zaphod.mps.ohio-state.edu> <4019@rex.cs.tulane.edu> <2501@l.cc.purdue.edu> <4060@rex.cs.tulane.edu> <3352@stl.stc.co.uk> <3788@osc.COM>
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In article <3788@osc.COM> jgk@osc.COM (Joe Keane) writes:
>I think returning a record just gets around the issue.  We don't use a single
>record to pass all the in parameters to a function, so why should we do it for
>out parameters?

In transformational programming (and, probably, elsewhere) it is often
convenient to assume that functions have just one argument (which may be
a tuple). So we *do* use a single record to pass all the in parameters
sometimes.

The problem of using a record for the out parameters is that the
function f below is not the identity function:

f(x) = 7*a+a where (a,a) = x/7

(assuming x/7 = (x DIV 7, x MOD 7))
but who would disagree to this being a (static) semantic error?

Eerke Boiten
Department of Informatics (STOP Project), K.U.Nijmegen
Toernooiveld, 6525 AD Nijmegen, The Netherlands
Tel. +31-80-612236.	Email: eerke@cs.kun.nl