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From: zben@umd5.UUCP (Ben Cranston)
Newsgroups: net.lang.c
Subject: Re:  Swap by name
Message-ID: <1065@umd5.UUCP>
Date: Mon, 7-Jul-86 18:37:23 EDT
Article-I.D.: umd5.1065
Posted: Mon Jul  7 18:37:23 1986
Date-Received: Wed, 9-Jul-86 02:09:14 EDT
References: <1964@brl-smoke.ARPA> <1060@umd5.UUCP> <2293@umcp-cs.UUCP>
Reply-To: zben@umd5.UUCP (Ben Cranston)
Organization: U of Md, CSC, College Park, Md
Lines: 26
Summary: OOPS

In article <1964@brl-smoke.ARPA> rbj@icst-cmr.ARPA (Root Boy Jim) writes:
> I was thinking of the caller squirrelling away the value in a temporary
> location, passing it by reference (thus allowing modification by the
> callee) and then copying the result to the real variable.

In article <1060@umd5.UUCP> zben@umd5.UUCP (Ben Cranston) replies:
> Of course the difference between this and real call-by-name comes when 
> the subroutine has an alternate access to the global in question - perhaps
> because of scoping rules, or access to a pointer-to-it or something.

In article <2293@umcp-cs.UUCP> chris@maryland.UUCP (Chris Torek) cautions:
> Careful, Ben: this was under a section about call by value-result,
> and it does accomplish that quite handily.

Er, yeah.  Another difference between call-by-name and value-result comes
when the actual is subscripted like a[i] and different array indices can
be selected on each reference to the formal (assuming i modified).  This
would have been a better example than the one I actually gave.   

No criticism of you or Root Boy was meant, I was only adding information.
Your point that I should have reviewed the entire discussion before posting
is well taken.
-- 
                    umd5.UUCP    <= {seismo!umcp-cs,ihnp4!rlgvax}!cvl!umd5!zben
Ben Cranston zben @ umd2.UMD.EDU    Kingdom of Merryland Sperrows 1100/92
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