OpenEuphoria

RE: 'Unknown' and three-valued logic (was: Example where Euphoria ...)

• Posted by rforno at tutopia.com Nov 29, 2002
• 521 views

Euler:
It seems to me you got the erroneous impression that I'm advocating for
3-valued logic. Not at all. I was only providing Rom with arguments against
it, on his request.
Oracle (I don't know if this is so for other data-base systems) has a
three-valued logic, and operations on it. Some years ago I worked with this
feature, but never found a practical use for it.
Be good...
----- Original Message -----
From: Euler German <efgerman at myrealbox.com>
Subject: RE: 'Unknown' and three-valued logic (was: Example where Euphoria
...)


>
> On 27 Nov 2002, at 18:28, rforno at tutopia.com wrote:
>
> >
> > For me, the main arguments against 3-valued logic are, in decreasing
order
> > of importance:
> > 1) It appears that there are few, if any, useful applications using this
> > kind of logic.
> > 2) These possible applications can be handled by ad-hoc routines and
data
> > types. For example, you may select 'F', 'T' and 'N' to represent the 3
> > values, and write 'not', 'and', 'or', 'xor', 'implication', etc.
routines to
> > compute the results.
> > 3) There is, to my knowledge, no universal consensus about the results
of
> > operations including 'nil', as the recent discussions in this list have
> > shown.
> > 4) For the application analyst and the programmer, it is much more
difficult
> > thinking in terms of 3 values and the respective operations.
> > 5) It is difficult to draw useful conclusions or actions from the
results in
> > 3-valued logic.
> > 6) While operations on strict Boolean logic are implemented very
> > efficiently, one cannot say the same about 3-valued logic. Especially
> > operations like and_bits, or_bits, etc., will suffer from severe
> > inefficiency.
> > 7) If, as suggested, a bit is reserved for 'nil' in each data item, then
the
> > representation ceases to be standard, and difficulties regarding
> > compatibility will arise.
> >
> > Regarding the examples, I think that they should be provided by the one
> > proposing this logic. Up to now, the examples provided by Rom have been
not
> > successful, in my view. The only example that can show a small benefit
was
> > (once more in my view) the very general one about its use in data bases
for
> > non-existing records or fields, particularly under Oracle, but even then
I
> > think it is only of theoretical importance, since I could not find a
> > convincing practical use for it.
> > Best wishes.
>
>
> I never had need of a 'third' logical boolean state. In fact, I don't
> believe it even exists, except as an abstraction. Note that this is
> just my opinion. The only other place where I found 'nil' referenced
> was on uninitialized variables (as in Lua).
>
> Taking Lua as example, variables have no need to be declared as string,
> number, table, etc. until it receives a 'value' of string, number,
> table, etc. This way, when created, any variable has a 'nil' (from
> Latin nihil - nothing) content. Lua also uses nil as boolean value but
> meaning FALSE. A boolean result in Lua can be 1 (TRUE) or nil (FALSE).
> There's no third stage. As in Euphoria, all variables must be declared
> and initialized before its use, there's no need of a 'nil' value, IMHO.
>
> Kind regards,
>
> -- Euler German
>
>
>
>