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From: kamal@wpi.WPI.EDU (Kamal Z Zamli)
Newsgroups: comp.lang.pascal
Subject: Re: Is this not a bug?
Message-ID: <1991Feb20.180329.21182@wpi.WPI.EDU>
Date: 20 Feb 91 18:03:29 GMT
References: <1991Feb20.170152.5401@ux1.cso.uiuc.edu>
Organization: Worcester Polytechnic Institute
Lines: 38

In article <1991Feb20.170152.5401@ux1.cso.uiuc.edu> mead@uxh.cso.uiuc.edu (Alan David Mead) writes:
>I finally tracked down a problem with an application writen in
>TP5.5:  Since my values are all positive, I used words instead of
>integers.  The ABS() function, however, does not operate as (I)
>expected with word parameters.  This code demonstrates.  While I
>can imagine how the value is produced by ABS(), I think the manual's
>description is deceptive.  What does the net think?
>============================================================
>program damnit;
>
>const
>  Start : integer = 900;
>
>var
>  w1,w2 : word;
>  i1, i2 : integer;
>
>  function Value:word;
>    begin
>      Start := Start - 200;
>      Value := Start;
>    end;
>
>begin
>  w1 := Value;
>  w2 := Value;
>  writeln( 'ABS( ',w2,' - ',w1,' ) =? ',abs( w2 - w1 ));
>
>  i1 := Value;
>  i2 := Value;
>  writeln( 'ABS( ',i2,' - ',i1,' ) =? ',abs( i2 - i1 ));
>end.

I might be wrong but I dont think you can change a constant.....and expect it 
to be the same again.. In order to avoid such problem just declare a dummy var
and assign it to var start each time the fucntion is called.

hope that help