[Haskell-cafe] Why is this strict in its arguments?

Andrew Coppin andrewcoppin at btinternet.com
Wed Dec 5 07:30:09 EST 2007

Luke Palmer wrote:
> On Dec 5, 2007 11:56 AM, Andrew Coppin <andrewcoppin at btinternet.com> wrote:
>> I was merely noting that questions of the form "is X decidable?" are
>> usually undecidable. (It's as if God himself wants to tease us...)
> I take issue with your definition of "usually" then.
> Whenever "X is decidable" is undecidable, "'X is decidable' is decidable' is
> decidable, namely false.  So there are at least as many decidable sentences
> of the form "X is decidable" as there are undecidable ones.

Ouch... my head hurts.

OK, well how about I rephrase it as "most 'interesting' questions about 
decidability tend to be undecidable" and we call it quits? ;-)

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