[Haskell-cafe] Re: Monads aren't evil? I think they are.
lrpalmer at gmail.com
Tue Jan 13 17:51:09 EST 2009
On Tue, Jan 13, 2009 at 11:21 AM, Tim Newsham <newsham at lava.net> wrote:
> I have seen several libraries where all functions of a monad have the
>> monadic result (), e.g. Binary.Put and other writing functions. This is
>> a clear indicator, that the Monad instance is artificial and was only
>> chosen because of the 'do' notation.
> Maybe that was the initial reason, but I've actually found the
> Binary.Put.PutM (where Put = PutM ()) to be useful. Sometimes
> your putter does need to propogate a result...
But that's the whole point of Writer! Take a monoid, make it into a monad.
Put as a monad is silly.
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