Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!uc!cs.umn.edu!rowley
From: rowley@cs.umn.edu (Henry A. Rowley)
Newsgroups: comp.lang.pascal
Subject: Re: TP 5.5  int() function
Keywords: TP,Turbo,Pascal
Message-ID: <1990Aug15.181830.5385@cs.umn.edu>
Date: 15 Aug 90 18:18:30 GMT
References: <1990Aug15.160719.12762@ux1.cso.uiuc.edu>
Distribution: comp
Organization: University of Minnesota, Minneapolis - CSCI Dept.
Lines: 27

In article <1990Aug15.160719.12762@ux1.cso.uiuc.edu> aindiana@osiris.cso.uiuc.edu (Daiv Stoner) writes:
>  rate:=2.01;
>  reg:=12.5;
>  value:=rate*reg*100+0.5;
>  x := int(value)/100;
>writeln('rate=',rate:8:4,'  reg=',reg:8:4,'  total=',rate*reg:8:4,'  x=',x:8:4);
>I get this output:
>
>rate=  2.0100  reg= 12.5000  total= 25.1250  x= 25.1200

It is probably a round off error.  You could verify the following statements
by printing the entire number, not a rounded version of it:  ie writeln(rate),
not writeln(rate:8:4).  Anyway, here is where the round off is occurring:

Lets say the actual value of rate is 25.124999999999999.  Then, if you multiply
by 100, you get  2512.49999999999.  Adding 0.5 gives 2512.999999999.  Then, 
truncate to the integer part of the number, and you get  2512.  Dividing by
one hundred gives you the final answer 25.12.  As you can see, this is due to
rounding errors, not a bug.

Henry A. Rowley          Internet: rowley@cs.umn.edu -or- rowley@ux.acs.umn.edu
THE CONTENT OF THE PROPOSITIONS - _The Shockwave Rider_ by John Brunner--------
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it, and since we can abolish them, we must.
#2:  That we are a civilized species.  Therefore none shall henceforth gain 
illict advantage by reason of the fact that we together know more that one of 
us can know.