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To find out, if a type is a higher kinded type ghci provide: 

Prelude> :k Maybe
Maybe :: * -> *

And tried on typeclass like: 

Prelude> :k Functor
Functor :: (* -> *) -> Constraint

Why can I ask for higher kinded type on typeclass? What does constraint mean?

duplode
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  • Closely related: [*What is Constraint in kind signature*](https://stackoverflow.com/q/29509786/2751851); [*What does has kind 'Constraint' mean in Haskell*](https://stackoverflow.com/q/41121107/2751851) (note the [second answer](https://stackoverflow.com/a/41123141/2751851) addresses your question more directly than the accepted one). – duplode Feb 24 '18 at 23:24
  • (I haven't closed as a duplicate myself because I'm not sure about which of the three questions would make for a better duplicate target, and also because your "Why can I ask for higher kinded type on typeclass?" might be hinting at a somewhat more general question. That being so, I will leave it up to you and/or the other readers to decide.) – duplode Feb 24 '18 at 23:26
  • I went ahead and closed this question as a duplicate. Is there any part of it that you feel the linked questions do not cover? – duplode Mar 05 '18 at 02:47

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