Haskell DC: A more general type for \f x → f (f x)

Noah Easterly demonstrates alternative types for a simple Haskell function literal and constructs a more general type that unifies them.

More information on the Haskell DC Meetup here: meetup.com/Haskell-DC/ Noah Easterly will give a talk titled "A More General Type For \f x → f (f x)". In Haskell, even a simple numeric literal has the polymorphic type of `Num a ⇒ a`, so it's no surprise that GHC can infer a polymorphic type for function literals like `\f x → f (f x)`. During this talk, we'll demonstrate other possible types for `\f x → f (f x)`, show that they're incompatible with the compiler inferred type, and then construct a more general type that unifies with all of these. This talk assumes only a basic knowledge of Haskell types, but will cover topics including higher-rank types, type unification/specialization, and defunctionalization.