Re: [Haskell-cafe] Proposal: Applicative => Monad: Call for consensus

On Tue, Jan 25, 2011 at 10:20 AM, Ketil Malde wrote:

Erik Hesselink writes:

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importing Control.Applicative

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main = print =<< liftM2 (+) readLn (return 3) [...] line noise

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Why not just:

main = print . (+3) =<< readLn

Or using applicative:

 print =<< (+3) <$> readLn

?

(Which separates the printing from the addition.)

-k

IMHO, all these proposed solutions just serve to further illustrate the problem. :-) Personally I don't mind having to use explicit combinators to interact with monadic values -- forces me to think things through, and all that -- but it's true that having automatic lifting would be convenient, and look less syntaxy. Alternatively, Disciple has effect typing and strictness-by-default rather than IO/ST monads, meaning you can use the same combinators to control functions with effects as you would for non-effectful functions, which is sort of like having automatic lifting for the IO and ST monads but not anything else (besides being a lot finer-grained).

-- If I haven't seen further, it is by standing in the footprints of giants

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