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

[Gábor Lehel]

On Tue, Jan 25, 2011 at 10:20 AM, Ketil Malde <ketil at malde.org> wrote:
> Erik Hesselink <hesselink at gmail.com> writes:
>
>>>> importing Control.Applicative
>
>>> main = print =<< liftM2 (+) readLn (return 3)
>>> [...] line noise
>
>> 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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