Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!olivea!mintaka!spdcc!tauxersvilli!alphalpha!nazgul
From: nazgul@alphalpha.com (Kee Hinckley)
Newsgroups: comp.sys.apollo
Subject: Re: The wonderful Pascal compilier...
Message-ID: <1990Nov14.031722.15456@alphalpha.com>
Date: 14 Nov 90 03:17:22 GMT
References: <43023@cci632.UUCP>
Organization: asi
Lines: 32

In article <43023@cci632.UUCP> mth@cci.com (Michael Hickman) writes:
>    while not((this_net = nil) or 
>              ((this_net^.plusminus = net.plusminus) and
>               (this_net^.net_name  = net.net_name))) do
>
>Looks like it tried evaluating the expression after the 'or' when the pointer 
>was nil.  I changed it to this:
...
>guru, so if anyone can shed some light on this, please do.  Otherwise, this is just
>another example of Apollo's great compilier technology.....

I wouldn't knock Apollo's compilers quite so fast.  The generate
pretty good code, even if they do take forever to do it.  But
any way, I believe you have run into a feature of Pascal.  Namely
that the order of expression evaluation is not guaranteed.  It's
been a while, but I believe that Apollo's Pascal has an 'andthen'
operator for just such cases, I assume there's something equivalent
for 'or', but I don't recall what.  Presumably 10.3 added some
compiler optimization or some such that made it decide it was
faster to interpret the expression some other way.

Now why you went into an infinite loop is another problem.  That
definitely sounds like a bug somewhere.

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I'm not sure which upsets me more; that people are so unwilling to accept
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everyone else's.