Path: utzoo!attcan!uunet!cs.utexas.edu!yale!eagle!rcook
From: rcook@eagle.wesleyan.edu
Newsgroups: comp.sys.mac.programmer
Subject: THINK Pascal expression quirk
Message-ID: <16954@eagle.wesleyan.edu>
Date: 12 Apr 90 11:17:17 GMT
Lines: 29

So this is what I had going on in THINK Pascal 2.0:

var
  x, a, b : integer;

begin
..
a := 400;
b := 500;
x := 11 + round( 248 * a / b );
..
end;

x was computed to be a negative number!  Do you see any minus signs above?  I
figured the '/' operator would force the whole expression inside round() to
evaluate as floating point numbers, but I suspect the compiler saw that '248*a'
was composed entirely of integers and computed an integer product, which
overflowed the range of an integer (though I didn't notice since I had range
checking off).  I changed the 248 to 248.0 and everything worked fine.  Big
deal?  Indeed, I should be using fixed point math anyway...

The next day I got THINK Pascal 3.0 and have not checked whether it has the
same quirk.

I just thought someone might be interested.  Beats drivel about upgrade prices
though :-)

Randall Cook
rcook@eagle.wesleyan.edu