Re: Alan Turing's Halting Problem is incorrectly formed (PART-TWO)
From: Daryl McCullough (daryl_at_atc-nycorp.com)
Date: 06/23/04
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Date: 23 Jun 2004 07:20:59 -0700
David C. Ullrich says...
>>> Peter Olcott says...
>>> >function LoopIfHalts (M, w):
>>> > if WillHalt (M, w) then
>>> > while true do {}
>>> > else
>>> > return false;
>There's more than one question here. What you just
>said _is_ the correct answer to the question of what
>LoopHalts() does. It follows from that that WillHalt
>is not giving correct answers about whether or not
>an arbitrary program halts.
Actually, Peter screwed up the counterexample. If you
are asking "Does LoopIfHalts halt?" you need to specify
the inputs. It has two input parameters, M and w. What
is Peter wanting M and w to be? Presumably, he wants
M to be the code for LoopIfHalts. But then what's w?
I think what he meant to write was something more like:
function LoopIfHalts(M):
if WillHalt (M, M) then
while true do {}
else
return false;
Then he would like to ask "Does LoopIfHalts halt when
given (the code for) LoopIfHalts as an input?"
--
Daryl McCullough
Ithaca, NY
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