Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!nrl-cmf!ames!ncar!tank!uxc!uxc.cso.uiuc.edu!zaphod!liberte
From: liberte@zaphod.ncsa.uiuc.edu
Newsgroups: comp.sys.mac.programmer
Subject: Re: Overflow Checking from within Pasca
Message-ID: <900010@zaphod>
Date: 10 Oct 88 22:30:00 GMT
References: <4276@polyslo.CalPoly.EDU>
Lines: 26
Nf-ID: #R:polyslo.CalPoly.EDU:4276:zaphod:900010:000:1260
Nf-From: zaphod.ncsa.uiuc.edu!liberte    Oct 10 17:30:00 1988


>	Overflow checking checks for integer overflow during computations,
>not during assignments. If you want to assign a large unsigned value
>to an integer variable, turn off the "R" compile option, or use {$R-}.

Wait a second.. You say I should turn off Overflow checking with the
Range checking option?  Of course, I should have guessed.  But in that case
what does {$V-} do?

Using R-V-, I still cannot turn off overflow checking for the following
expression: 128 * 256
But, in a way, I was glad I couldnt because it was my error to not
cast to a longint.  The only reason I had tried to turn
off this overflow check was because it was part of an unsigned integer
assignment.  (The smallest gradularity for changing overflow checking is
the line since one cannot put comments in the middle of lines.)

While I am at it, it is not possible to put comments in the Observe window
to affect how that code is compiled.  Thus I cannot easily debug code
that depends on turning off range checking, for example.  A case in point,
cSpecArray is declared as an Array [0..0] of ColorSpec because it is
of variable length.  Aside from the difficulty of using this in code,
the Observe window does not allow any other index but 0 which is not
very useful.

Dan LaLiberte