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From: phils@chaos.cs.brandeis.edu (Phil Shapiro)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Why can't the Mac add?
Message-ID: <PHILS.90Sep25183555@chaos.cs.brandeis.edu>
Date: 25 Sep 90 22:35:55 GMT
References: <45060@apple.Apple.COM> <20360@dime.cs.umass.edu>
	<45108@apple.Apple.COM> <1990Sep25.174006.11979@agate.berkeley.edu>
Sender: @chaos.cs.brandeis.edu
Organization: Symantec Corp.
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In-Reply-To: lindahl@violet.berkeley.edu's message of 25 Sep 90 17:40:06 GMT

In article <1990Sep25.174006.11979@agate.berkeley.edu> lindahl@violet.berkeley.edu (Ken Lindahl   642-0866) writes:
   In article <45108@apple.Apple.COM> das@Apple.COM (David Shayer) writes:
   >huh-HUM (throat clearing noises.)
   >The calculator DA can do this math correctly.  If you add 0.2 fifty
   >times, you get 10.0.  Exactly.  Not 9.999999 or 10.0000001.  I tried
   >changing my float variable to an extended, as someone suggested.  No dice.
   >Does the calculator DA have its own special math package?  (If so, the
   >dCad calculator does too.)  No one seems to think SANE has calls which
   >take care of this.  So why does it work in the calculator?
   >
   >David

   huh-HUM (throat clearing noises.)

   [ description of how Calculator truncates floats ]

   Ken Lindahl				lindahl@violet.berkeley.edu

I don't know if this has any bearing, but I just tried out adding .2
to itself 10 times, got '2', then subtracted '2'.  The result?
2.168404E-19.  Go figure :-)

	-phil
--
Phil Shapiro
phils@chaos.cs.brandeis.edu