[Haskell-cafe] Plain lambda inside banana brackets in the arrow notation

Ertugrul Söylemez es at ertes.de
Sun Jul 15 20:22:07 CEST 2012

Ross Paterson <ross at soi.city.ac.uk> wrote:

> Though one possibility that might get us most of the way there would
> be to refactor the Arrow class as
>   class PreArrow a where
>     premap :: (b -> b') -> a b' c -> a b c

Note that you are reinventing the 'profunctors' package here.  Every
arrow forms a profunctor with the following identities:

    lmap = flip (<<^)
    rmap = fmap

or alternatively:

    rmap = (^<<)


Not to be or to be and (not to be or to be and (not to be or to be and
(not to be or to be and ... that is the list monad.
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