> A *much* simpler version is f'(x) = {-1 if x<0; +1 if x>0; Chaitin's constant ... | Hacker News

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ogogmad 5 months ago | parent | context | favorite | on: Non-computability of solutions of certain equation...

> A much simpler version is f'(x) = {-1 if x<0; +1 if x>0; Chaitin's constant if x=0}. f(x) = abs(x).

This is wrong. The function f you've defined is not continuously differentiable. The one in Myhill's paper is.

a1369209993 5 months ago [–]

Evidently I should have been more explicit:

> > A much simpler[-and-more-nitpickable] version

Myhill uses a parlor trick to make his version continuously differentiable. It's a pretty good parlor trick, but it doesn't have much to do with computability.

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