Dear Roy,
Perhaps the following might provide a clue to other participants in
this forum why your posts are relevant to J or at least remind people
of why a most prestigious honour that Dr Ken Iverson was given was
named for Allan Turing
In response to Hibert's question, Gödel, Church, Tarsky & Turing all
contributed to demonstrating what a computer language could and
couldn't be:
Here is an online source that happens to be free, tho of course
subject to copyright
Turing's famous 1936-7 paper On computable numbers, with an
application to the Entscheidungsproblem, which worked out the theory
of Turing machines and the definition of computability, is available
as a PDF file on-line
American Mathematical Society page explaining Turing machines.
Wolfram Research page on Turing machines.
and also
What Gödel saw
Kurt Gödel's 1931 incompleteness theorem rewrote the agenda in the
foundations of mathematics.
The Gödel home page is extended to an exhibition to mark Gödel's
centenary year.
Donna
[EMAIL PROTECTED]
On 20-Jun-06, at 11:45 PM, Roy A. Crabtree wrote:
Look up the value "undefined" in te J dictionary.
And then program so as to avoid placing any other meaning on it.
Thus, whenever you encounter it in a J computation, it would
indicate your failure to program properly.
And provide an immediate fence post to wht I call eigenstate collape:
Your program has no proper meaning at that point relativ to your
original attempted solution.
More importantly, make sure that every computation made strays
fully _within_ all relevant bounds (size, null vectors, unasigned
values, over- and under-flow
AS WELL AS other numerical analysis failures, not too uch and not
too little randomness if involved, and so on).
Only the _implementor_ can ascertain and attempt to denote failures
of these constraints, and only the implementor
has a chance to actually ASSIGN an "undefined" value if these
bounds are transgressed.
The same philosophy already exists in J's design, which is why so
many o fthese errors are inherently avoided:
because it is just that much harder to MAKE uch an error in J.
Because J tends to _correctly_ implment _Mathematocs_ correctly
so much more of the time.
BUT not all if the time, and cetainly J cannot maintain the _inent_
a program is intended to obey by its mplementor.
THAT has to be done by the programmer. By specific conscious
ongoingh effort at maintaing the intent to _correctly_ keep the
purpose of
the program intact at all times.
Very hard to do in any non-simple program.
Hrd enough even in the simple ones.
On 6/20/06, dly <[EMAIL PROTECTED]> wrote:
By undefined in J
do you mean a variable to which no value has been assigned?
an attribute that is defined for some but not all?
is it associated with something like null which you can test for?
how does J handle the undefined?
Donna
[EMAIL PROTECTED]
On 20-Jun-06, at 9:51 PM, dly wrote:
> For the beginner in J
>
> can you point me to a help reference to the undefined in J ?
>
> Re: Schroedinger's Qat--and I always thought he was talking about a
> cat--this puts things in entirely new purple haze.
>
> Donna
> [EMAIL PROTECTED]
>
>
>
> On 20-Jun-06, at 9:30 PM, Roy A. Crabtree wrote:
>
>> which is why the undefined value in J is so important.
>>
>> It corresponds roughly to the Aisan concept of yes, no, _mu_:
>
>> Schroedinger's Qat being neither dead nor alive until someone
>> looks to see.
>>
>
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
--
--
Roy A. Crabtree
UNC '76 gaa.lifer#11086
Room 207 Studio Plus
123 East McCullough Drive
Charlotte, NC 28262-3306
336-340-1304 (office/home/cell/vmail)
704-510-0108x7404 (voicemail residence)
[EMAIL PROTECTED]
[EMAIL PROTECTED]
[EMAIL PROTECTED]
http://www.authorsden.com/royacrabtree
http://skyscraper.fortunecity.com/activex/720/resume/full.doc
--
(c) RAC/IP, ARE,PRO,PAST
(Copyright) Roy Andrew Crabtree/In Perpetuity
All Rights/Reserved Explicitly
Public Reuse Only
Profits Always Safe Traded
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
