

Proof in Functions - mbrandonw
http://www.fewbutripe.com/swift/math/2015/01/06/proof-in-functions.html

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Chinjut
Of note: The definition given of propositional implication is in terms of
classical Boolean logic, but, though I don't know much about Swift, it seems
likely from the discussion that its inhabitable types correspond to the
theorems of intuitionistic logic rather than classical logic. [E.g., it is
unlikely to be possible to implement generic functions of types such as "((P
-> Q) -> P) -> P" or "Not<Not<P>> -> P", despite these being Boolean
tautologies (these are often thought of as in Curry-Howard correspondence with
constructs like call/cc, which perhaps is an integral component of Swift, but
at any rate, this nuance was never discussed in the article)].

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mbrandonw
I do address this, but in the exercises at the end. Decided to cut a
discussion on intuitionistic logic.

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Chinjut
My apologies; I don't know how I missed that. This obviates my original
comment.

