[Haskell-cafe] Re: what is inverse of mzero and return?
k.schupke at imperial.ac.uk
Mon Jan 24 13:18:31 EST 2005
Ashley Yakeley wrote:
>If you remember your category theory, you'll recall that two morphisms
>are not necessarily the same just because they're between the same two
>objects. For instance, the objects may be sets, and the morphisms may be
>functions between sets: morphisms from A to B are the same only if they
>map each element in A to the same element in B.
Yes, but I though the 'objects' in this case are endofunctors from a
type to itself... the the morphisms operate on these endofunctors, the
morphisms are unit and join.... such that joining 'unit' to the
endofuntor retults in the endofunctor.
But I think that as the endofunctor is from the type to itself, the
value does not
come into it.
A -> A `join` unit => A -> A
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