Errata
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29 July 2010
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Typos: "to" should be deleted in the second line of Section 1. "that
that" somewhere.


29 July 2010
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Luke Palmer rightly pointed out that "p True" is just as lazy as "if p
True then True else False", contrarily to what is claimed in the paper
He argued operationally. But this is also easy to see denotationally:
The only potentially problematic case is when p(bot) = b /= bot. In
this case both expressions return b. The same applies to a similar
remark about the expression "p True < p False" in the paper.

11 August 2010.
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Phil Wadler pointed out that the equation "findnot = find.not" is not
quite correct, and that it should have been instead "findnot xs p =
find xs (not.p)".

12 August 2010.
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Typos: f_n should be f_k in item 2 about optimal strategies in Section
4.1.

12 August 2010.
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"[Compact] sets of total elements form countably based Hausdorff
spaces": the word "compact" is missing in the original. Without
compactness, the Hausdorff property still holds, but the countability
condition fails in general.