From: John Deters <jad@dsddhc.com>
Date: Thu, 23 May 1996 11:04:27 +0800
To: cypherpunks@toad.com
Subject: Re: The Crisis with Remailers
Message-ID: <2.2.32.19960522214836.003432fc@labg30>
MIME-Version: 1.0
Content-Type: text/plain


At 12:14 PM 5/22/96 -0400, Perry wrote:
>
>Matts Kallioniemi writes:
>> At 17:44 1996-05-21 +0200, bryce@digicash.com wrote:
>> >Matts, you don't want to do floating point for money, because
>> >floating point doesn't give you good control of precision.
>> 
>> Yes I do. Several major currency traders in Sweden keep all
>> their money in 64 bit floating point storage.
>
>I have trouble believing you. None of the forex accounting I know of
>in the U.S. is done in floating point. It simply isn't accurate
>enough.
>
>It is true enough that *rates* can be stored as floats if you want,
>but never actual sums.

I wish there were a hard-and-fast rule that this were true.  I work in
Point Of Sale (POS or cash registers), and occasionally we will see a vendor
whose software stores money/currency in floating point data types.  I try
very hard to make sure we do not purchase their software, because this
implies the most gross lack of understanding imaginable.

Floating points are simply not accurate when you're performing math on
other people's money.

And, yes, rates are acceptable to store and use as floats, but even the
conversion process ultimately yields a long, not a float.  And, we usually go
out of our way to code rates up as integers and perform the decimal point
shifting in code.

In the currency class we use, we have an exponent property that defines where
the decimal point is.  I imagine that by converting the exponent from a short
to a long we could even handle lira!  :-)  *

* Note to persons who respect the Italian economy**:  That was a joke!

** Note to persons who believe there are people who respect the Italian economy:
   That was a joke!

-john
--
J. Deters
>From Senator C. Burns' Pro-CODE bill, which I support and you can find at:
http://www.senate.gov/member/mt/burns/general/billtext.htm
"  (2) Miniaturization, disturbed computing, and reduced transmission
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