[Haskell-beginners] Trying to prove Applicative is superclass of Functor, etc
Dániel Arató
exitconsole at gmail.com
Fri Apr 29 09:23:23 UTC 2016
Applicative is actually a *sub*class of Functor. :)
> Hi, well aware it's trivial so I'll be terse: do we have?:
>> fmap = <*> . pure
That's right. You have to wrap the "<*>" in parantheses though.
> So we could write for example
>> liftA2 f fa fb = f <$> fa <*> fb
> this way?:
>> liftA2 f fa fb = pure f <*> fa <*> fb <*>
You don't need the last "<*>", but other than that yeah, that's exactly right.
> Incidentally, do we have?:
>> liftA == liftM == fmap
Correct. The Prelude defines liftM in terms of do notation though for
reasons that escape me. But it's basically just fmap.
Daniel
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