Very comfortable to understand function composition! #CodePiece #tryswiftnyc

CodePiece.swift

precedencegroup FunctionApplication {
    associativity: left
    higherThan: AssignmentPrecedence
}

infix operator |>: FunctionApplication

func |> <A,B>(a: A, f: (A) -> B) -> B {
    return f(a)
}

// 2.incr().square()
let x = 2 |> incr |> square // |> String.init

precedencegroup FunctionComposition {
    associativity: left
    higherThan: FunctionApplication
}

infix operator >>>: FunctionComposition

// f // (A) -> B
// >>>
// g //       (B) -> C
// -> ================
//      (A)    ->    C

func >>> <A, B, C>(
    f: @escaping (A) -> B,
    g: @escaping (B) -> C)
    -> (A) -> C {
    return { g(f($0)) }
}