How to map value in tuple #CodePiece #tryswiftnyc

CodePiece.swift

func mapFirst<A, B, C>(
    _ f: @escaping (A) -> B)
    -> ((A, C)) -> (B, C) {
        return { pair in (f(pair.0), pair.1) }
}

let incrFirst2: ((Int, String)) -> (Int, String) = mapFirst(incr)

pair |> mapFirst(incr)

func mapSecond<A, B, C>(
    _ f: @escaping (A) -> B)
    -> ((C, A)) -> (C, B) {
        return { pair in (pair.0, f(pair.1)) }
}

pair
//    |> mapFirst(incr)
//    >>> mapFirst(square)
//    >>> mapFirst(String.init)
    |> mapFirst(incr >>> square >>> String.init)
    >>> mapSecond { $0.count }

mapFirst(incr)
    >>> mapFirst(square)
    >>> mapFirst(String.init)
    >>> mapSecond { (str: String) in
        str.count }

let nested = ("Hello", (42, "World"))

nested |> mapSecond { second in
    second |> mapFirst { first in
        incr(first)
    }
}