Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!iuvax!maytag!watstat!dmurdoch
From: dmurdoch@watstat.waterloo.edu (Duncan Murdoch)
Newsgroups: comp.lang.pascal
Subject: Re: HELP with Turbo Pascal problem
Keywords: Turbo Pascal
Message-ID: <1092@maytag.waterloo.edu>
Date: 6 Jan 90 05:34:41 GMT
References: <3433@tahoe.unr.edu>
Sender: daemon@maytag.waterloo.edu
Reply-To: dmurdoch@watstat.waterloo.edu (Duncan Murdoch)
Organization: U. of Waterloo, Ontario
Lines: 23

In article <3433@tahoe.unr.edu> rfh@unssun.nevada.edu  (J.A. MacDonald) writes:
>HELP!!
>
>  I wrote the following program in TurboPascal 5.5 and got a very
>wrong answer. One would expect to get an output value for j of 64516,
>but instead get -1020. 
...
>  i : integer;
>  j : real;
>
>begin 
>  i := 254;
>  j := i * i;

You got what you're supposed to get, according to the specs for TP.  It 
evaluates ordinal expressions in the smallest type that will hold the 
operands; thus i * i is evaluated as an integer, and it overflows before it
gets converted to real and stored in j.  You can get the result you expect 
by using
   j := i * longint(i);
or something similar, to force the calculation to take place as a longint.

Duncan Murdoch