[Haskell-beginners] Monad for Pair
mike_k_houghton at yahoo.co.uk
Wed Nov 18 18:33:59 UTC 2015
'Much better if you let us know the source of this problem. Is this an exercise from some book / online course?”
The source is just me exploring.
I first looked at
data C a = C a deriving (Show)
and made Monad, Applicative, Monoid and Functors for it.
So then tried
Pair a = P (a, a)
and stuck on Monad.
> On 18 Nov 2015, at 07:23, Kim-Ee Yeoh <ky3 at atamo.com <mailto:ky3 at atamo.com>> wrote:
> On Wed, Nov 18, 2015 at 4:41 AM, Mike Houghton <mike_k_houghton at yahoo.co.uk <mailto:mike_k_houghton at yahoo.co.uk>> wrote:
> And really return x = P (x, x) doesn’t seem correct anyway.
> But if you look at the type, which is essentially "a -> (a,a)" there's only one way to write it, for the same reason that there's only one "a -> a" function.
> Would someone please write the Monad with an explanation?
> Much better if you let us know the source of this problem. Is this an exercise from some book / online course?
> -- Kim-Ee
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