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scala> :kind scala.Option
scala.Option's kind is F[+A]
scala> :k (Int, Int) => Int
scala.Function2's kind is F[-A1,-A2,+A3]
scala> :k -v Either
scala.util.Either's kind is F[+A1,+A2]
* -(+)-> * -(+)-> *
This is a type constructor: a 1st-order-kinded type.
scala> :k -v scala.collection.generic.ImmutableSortedMapFactory
scala.collection.generic.ImmutableSortedMapFactory's kind is X[CC[A,B] <: scala.collection.immutable.SortedMap[A,B] with scala.collection.SortedMapLike[A,B,CC[A,B]]]
(* -> * -> *(scala.collection.immutable.SortedMap[A,B] with scala.collection.SortedMapLike[A,B,CC[A,B]])) -> *
This is a type constructor that takes type constructor(s): a higher-kinded type.
scala> :k new { def empty = false }
AnyRef{def empty: Boolean}'s kind is A
scala> :k Nonexisting
<console>:12: error: not found: value Nonexisting
Nonexisting
^
scala> :quit
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