[Haskell-cafe] Article review: Category Theory

David House dmhouse at gmail.com
Thu Jan 18 12:05:28 EST 2007

On 18/01/07, Joachim Breitner <mail at joachim-breitner.de> wrote:
> But if _|_ can take on any type, it can take on a -> b. And in what way
> does it then differ from \x -> _|_?

_|_ is bottom.
\x -> _|_ is a function that takes a value and returns bottom.

You can tell them apart, using seq, as Neil showed, but apart from
that I guess they're unique. If you had:

f = undefined
g = \x -> undefined

Then f x = g x for all x.

-David House, dmhouse at gmail.com

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