[Haskell-beginners] Re: Either Monadic Trouble

Ertugrul Soeylemez es at ertes.de
Mon Nov 9 15:44:44 EST 2009

Nicolas Pouillard <nicolas.pouillard at gmail.com> wrote:

> > Either is not a monad, you can check this by typing
> >    :i Either
> > in GHCi; you will not see a line like
> >    instance Monad Either
> > in the result. Compare this to
> >    :i Maybe
> In fact the Either Monad instance is defined in the 'transformers' (or
> 'mtl') packages.

Either is still not a monad.  Have a look at its kind.


nightmare = unsafePerformIO (getWrongWife >>= sex)

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