On 5/15/2011 5:36 PM, Terry Reedy wrote:
On 5/15/2011 1:33 PM, rusi wrote:
Dijkstra's writings I alluded to,
at
http://www.cs.utexas.edu/users/EWD/transcriptions/EWD10xx/EWD1070.html
"Acquiring that familiarity requires what in these financial times is
known as "intellectual investment"; you can take my word for it that
this investment quickly pays off."
I recommend understanding the following as three more "intellectual
investments":
We create a Boolean domain by drawing a distinction in some domain and
treating everything on each side of the distinction as equal in some
value. A Boolean value or variable represents such a dichotomy, a choice
between two all-inclusive but mutually exclusive possibilities. Boole
derived his domain from truth/falsity of propositions. But that is an
interpretation of his abstract model and only one of endless possibilities.
This realization that switching networks are another interpretation is
the basis of digital computation. Boolean algebra theorems are theorems
about switching networks and can be used to design such networks. Such
networks can be used to do boolean arithmetic. The trick is to coerce
physical components into one of two states. Part of the trick is to not
look when they are transiting between them.
For its built-in information objects, Python choose 'representation of
something' versus 'representation of nothing' as the dichotomy. It
matches 'something' to True and 'nothing' to False as this is generally
more useful than the opposite matching. In boolean contexts, it
automatically fetches the boolean value of an object.
--
Terry Jan Reedy
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