[Haskell-cafe] Another monad question...

[David LaPalomento]

On 7/15/07, Miguel Mitrofanov <miguelimo38 at yandex.ru> wrote:
>
> SOR> I've heard that Monads are in some way like Monoids, hence the
> SOR> name. But I don't understand the explanation yet myself :(
>
> Just compare:
>
> Monoid: a set M with maps ident: M^0 -> M and product: M^2 -> M
>
> (here M^0 is a one-element set)
>
> Monad: a functor M with natural transformations return: M^0 -> M and
>        join: M^2 -> M
>
> (here M^0 is an identity functor)


I had forgotten that the identity element was from M^0 -> M.  In my gut I
always feel it should be something more like M -> M, though I realize (as
Stefan pointed out) I'm thinking too much in set-terms and not in
category-terms.

David
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