What does λ[α =>F] mean?

Question

I'm learning Scalaz recently. I would like to know how λ[α =>F] works?

scala> Applicative[λ[α => Int]].point(10)
res45: Int = 0

scala> Applicative[λ[α => String]].point(10)
res46: String = ""

I can understand λ means some type here, but I could not find its definition and would like to know how the above code works.

Lambda that takes a (anything) and returns an Int (first one) or a String (second one). If you come from imperative programming you can think of it as a pointer to a function int foo(Object a) and string foo(Object a). But don't tell functional programmers that you think this way, they tend to get angry. — v010dya, Sep 21 '15 at 04:44
Thanks! I'd like to know how the λ type works, There must be some code about the λ. Because I could not change λ to a different name, such as T. Applicative[T[α => String]].point(10) does not work — Binzi Cao, Sep 21 '15 at 04:56

score 2 · Accepted Answer · answered Sep 21 '15 at 07:17

2

scalaz use kind-projector.

Applicative[λ[α => Int]] is equivalent to Applicative[({type l[a] = Int})#l]

answered Sep 21 '15 at 07:17

Kenji Yoshida

1 Answers1