[Haskell-beginners] Empty type

[Kim-Ee Yeoh]

On Sat, Oct 26, 2013 at 12:26 AM, Nicholas Vanderweit <
nick.vanderweit at gmail.com> wrote:

> Or, alternatively, using fix from Data.Function:
>
> fix NotVoid
>

Yes, and all of them are indistinguishable from bottom or 'undefined ::
forall a. a', the ghost that inhabits all types, including the empty one:
Void.

What trips up beginners is the interpretation of indistinguishable-ness. At
the level of denotational design, 'undefined' and 'error "(sadface)"' are
to be treated as equal, although beginners would point out: "hey look, I
get different output!"

Call it denotational design, or call it beautiful FP modelling, this stuff
is really where it's at.

-- Kim-Ee
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