Path: utzoo!mnetor!uunet!husc6!cmcl2!brl-adm!umd5!purdue!i.cc.purdue.edu!k.cc.purdue.edu!l.cc.purdue.edu!cik
From: cik@l.cc.purdue.edu (Herman Rubin)
Newsgroups: comp.lang.misc
Subject: Re: multiple values
Message-ID: <734@l.cc.purdue.edu>
Date: 30 Mar 88 17:43:55 GMT
References: <12176@brl-adm.ARPA> <1988Mar11.215238.976@utzoo.uucp> <3213@haddock.ISC.COM>
Organization: Purdue University Statistics Department
Lines: 31
Summary: But how should it be done

In article <3213@haddock.ISC.COM>, karl@haddock.ISC.COM (Karl Heuer) writes:
> In article <727@l.cc.purdue.edu> cik@l.cc.purdue.edu (Herman Rubin) writes:
> >In article <3177@haddock.ISC.COM>, karl@haddock.ISC.COM (Karl Heuer) writes:

> So?  The way I wrote it, q and r are never more than unnamed virtual objects.
> I'm looking for a syntax that allows all three (qr, q, r) to disappear, if
> all I really want is an expression that returns q*q+r*r.  If we allow 2-d
> notation, this could be written

This shows that flexibility and non-portability are needed.  If the quotient 
and remainder are not simultaneouly generated, then the choice between the
order of computation is quite great, while if the hardware simultaneously
can generate them, and registers can hold the information, the pair (q,r)
as a real object should exist for the purpose of reasonable efficiency.  In
the case where the programmer or compiler wishes to use that capability of the
hardware, it is necessary to have an object which I call a list.  Namely, the
operation returns more than one value, and there is no necessary relation 
between the locations of the various objects. 

If the hardware insists in putting the quotient and remainder in adjacent
registers, this in no way complicates matters.  Typically, the user will
allow an optimizing compiler to take these things into account.  If the
compiler is not sufficiently optimizing, the user will have to edit the
compiler's output.  But the language which does not have lists is unlikely
to be able to act reasonably if they are useful.
inter

-- 
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907
Phone: (317)494-6054
hrubin@l.cc.purdue.edu (ARPA or UUCP) or hrubin@purccvm.bitnet