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From: ags@s.cc.purdue.edu (Dave Seaman)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Turbo Pascal - Am I Nuts?
Message-ID: <3437@s.cc.purdue.edu>
Date: 25 Jul 88 00:58:55 GMT
References: <7536@cup.portal.com>
Reply-To: ags@s.cc.purdue.edu.UUCP (Dave Seaman)
Organization: Purdue University
Lines: 40

In article <7536@cup.portal.com> Mike_G_Newman@cup.portal.com writes:
>In 'How to Write Macintosh Software', Scott Knaster says that I 
>can do something like this:
>
>     errCode := FSRead(fileRefNum,count,thisMemberHdl^);
>
>However, Borland's Turbo Pascal wants me to do this:
>
>     errCode := FSRead(fileRefNum,count,@thisMember);
>
>Can someone explain this to me?  Who's right?  Are there other 
>problems with the Turbo compiler?

I think you will find that both methods work just fine with Turbo.  I
assume your declarations are something like

	type

	  aMemberHdl = ^aMemberPtr;
	  aMemberPtr = ^aMember;

	  aMember    =  ... something or other ...

	var

	  thisMemberHdl : aMemberHdl;
	  thisMember    : aMember;

so that the expressions ``thisMemberHdl^'' and ``@thisMember'' are both
the same type (i.e. aMemberPtr) and therefore interchangeable so far as
the rules of Pascal are concerned.  The ``@'' sign in Turbo, unlike
standard Pascal, is an ``address-of'' operator (similar to ``&'' in C).  As
long as you remembered to allocate the handle before the call, it should
make no particular difference which way you do it.  There is sometimes an
advantage in allocating structures on the stack rather than the heap so as
to avoid heap fragmentation.

-- 
Dave Seaman	  					
ags@j.cc.purdue.edu