[Haskell-cafe] Re: what is inverse of mzero and return?
ashley at semantic.org
Tue Jan 25 05:24:30 EST 2005
In article <41F61A0B.90005 at imperial.ac.uk>,
Keean Schupke <k.schupke at imperial.ac.uk> wrote:
> I am sure monads in Haskell (and other functional languages like ML) are
> defined on types not values.
The objects of the category are types. The morphisms on the category are
functions. Two functions are the same if they match each value to the
same value. For the Functor laws and the Monad laws, the values
certainly do matter: if they didn't, they wouldn't correspond to the
category theory notions of functor and monad because the morphisms would
Ashley Yakeley, Seattle WA
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