On Fri, Sep 14, 2012 at 9:08 PM, Andrew Pennebaker <andrew.pennebaker@gmail.com> wrote:

Given that Maybe and Either don't modify state, nor do they communicate with outside interfaces, nor do they specify computation ordering, I don't understand why they're implemented as monads. Why not a primitive typeclass or even datatype declaration?

They're not used in their monadic guise as often as they should be, IMO. Either String has for a while been an "error monad" (more commonly, EitherT String as ErrorT) but has annoying shortcomings --- but they're an obvious mechanism for reporting and tracking / short-circuiting failure in computations (carrying a failure reason in the case of Either).

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brandon s allbery allbery.b@gmail.com
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