Proposal for modifying gnucash to use exact quantities

[Richard Wackerbarth]

On Wed, 02 Aug 2000, Buddha Buck wrote:
> > On Wed, 02 Aug 2000, Buddha Buck wrote:
> > > I view "$/8 USD" and "$/100 USD" to be -similar- commodities.  You
> > > can't add or subtract them, but comparison should be possible. 
> > > Conversion between them is possible without an explicit conversion
> > > ratio -- the ratio is implicit.  They probably don't have the same
> > > display function.
> > >
> > > Is there a sensible way to include that concept?
> >
> > An interesting concept (comparing two values without being able to
> > express their difference). Where do you see that it might be useful in
> > financial transactions?
>
> I'm not sure that I do.  Comparison might not be a useful property,
> although I
> think $/8 USD and $/100 USD are fundamentally easier to compare than
> $/8 USD and $/8 CND.  The important property to me ws the implicit
> conversion ratio.

As I see it, we seem to have some implicit common currency that we use as the 
"native" currency for a particular set of books. Here in the USA, it would be 
USD, but in Canada, it would probably be CDN. In either case, if I have one 
account in each currency, I would report the "value" in the native currency.
We implicitly convert from CDN to USD in order to generate a "total 
(estimated) value" of the accounts. Similarly, if I have an account of Redhat 
stock, I apply an exchange rate to convert to a cash value.

By the same conversion, I can convert from $/8 USD to the native currency and 
from $/8 CND to the native currency, and from $/100 USD to the native 
currency. Therefore, by simply concatenating two exchange rates I should be 
able to have the exchange rate between any two accounts for estimation 
purposes.

> > > What I'd like is to be able to specify to the conversion routine two
> > > commodities and a price without having to worry about conversions
> > > within USD or whatever.  Being able to be told that $50 2/8 USD, at
> > > $1.50 CND/$1.00 USD, is $75 3/8 without having to specify that $1 0/8
> > > USD = $1.00 USD and $1 0/8 CND = $1.00CND would make dealing with
> > > exchange-rate tables -much- easier.
> >
> > I'm not sure that I agree. I think that you DO need to specify the 1 0/8
> > USD = $1.00 USD somewhere ONCE. After that, that fact should be
> > implicitly available.
>
> My thought would be that it would be implied by the denominators that
> 8 USD/8 = 100 USD/100, and that would be the implicit conversion ratio.

Is this not just an artifact of the commonality of a parent currency?