Re: Perl source filter question

[David Steuber <david.steuber@verizon.net>]

On Fri, Oct 10, 2003 at 11:56:50PM -0400, mjd-perl-pm@plover.com wrote:
> The halting theorem is a special case of Rice's theorem.  The proof is
> similar.  
> 
> The halting problem theorem says that there is no general way to tell,
> by examining a program, whether it will halt on a particular input.
> 
> Rice's theorem says that there is no general way to tell, by examining
> a program, *any* property of its behavior, unless the property is
> completely trivial.  (A property is 'trivial' either if every
> program has the property or if no program has the property.)

Thanks for the extra info.  I had no idea that there was a special name
for what I always thought of as an obviouse general case.  After all,
the halt could be a function that a program calls either explicitly or
implictly on exit.  s/halt/any_function/ seems natural to me.

In the case of Perl, I remember putting function names into variables to
generate 'dynamic' calls.  ie:

  $func = a_method;
  $foo->$func($arg);

Or something like that.  Pardon me if syntax is wrong.  It was a while
ago so I forget the precise details.  In any case, 'eval' was not
required for dynamic dispatching or whatever you want to call that
technique.

There was an intersting article on "The Omega Man":

  http://www.dc.uba.ar/people/profesores/becher/ns.html

It is a rather interesting read.  My only problem with it is that I
thought this number to already be known about, so to speak, from the
proof that the set of transendental numbers is larger than the set of
algebraic numbers inside the set of all numbers.  I wish I remembered
the name of the book I read that in.  Circa WWII publication on
mathematics.

I wish I remembered my math.  When I am not distracted by shiny things,
which happens more than you might think, I am playing with Lisp (Emacs
    and Common).  Basic math is really nice to know.  I've got all my
math books on hand to try and pick it back up.  The problem of course is
all the shiny things around.

The PowerBook should not have been made with an aluminum case.  At the
least, it should have been anodized black.  Then again, that probably
wouldn't help much.  Er, I mean that GNU Emacs from:

  pserver:anoncvs@subversions.gnu.org

builds nicely on OS X 10.2.8 as does Perl 5.8.1.

Math has defined the limits of knowledge.  The demand of Magicthighs has
been met.  We have rigidly defined areas of doubt and uncertainty.
Isn't life grand?

-- 
David Steuber           |  telco:610.436.1677
302 E Marshall St       |  http://www.david-steuber.com/
Apt 612                 |  (do ((a 1 b) (b 1 (+ a b)))
West Chester, PA 19380  |      (nil a) (print a))
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