I think F#'s pipe forward operator (|>) should vs (&) in haskell.

// pipe operator example in haskell

factorial :: (Eq a, Num a) =>  a -> a
factorial x =
  case x of
    1 -> 1
    _ -> x * factorial (x-1)

// terminal
ghic >> 5 & factorial & show

If you dont like (&) operator, you can custom it like F# or Elixir :

(|>) :: a -> (a -> b) -> b
(|>) x f = f x
infixl 1 |>

ghci>> 5 |> factorial |> show

Why infixl 1 |>? See the doc in Data-Function (&)

infixl = infix + left associativity

infixr = infix + right associativity

(.)

(.) means function composition. It means (f.g)(x) = f(g(x)) in Math.

foo = negate . (*3)

// ouput -3
ghci>> foo 1
// ouput -15
ghci>> foo 5

it equals

// (1)
foo x = negate (x * 3) 

or

// (2)
foo x = negate $ x * 3 

($) operator is also defind in Data-Function ($).

(.) is used for create Hight Order Function or closure in js. See example:

// (1) use lamda expression to create a Hight Order Function
ghci> map (\x -> negate (abs x)) [5,-3,-6,7,-3,2,-19,24]  
[-5,-3,-6,-7,-3,-2,-19,-24]


// (2) use . operator to create a Hight Order Function
ghci> map (negate . abs) [5,-3,-6,7,-3,2,-19,24]  
[-5,-3,-6,-7,-3,-2,-19,-24]

Wow, Less (code) is better.

Compare |> and .

ghci> 5 |> factorial |> show

// equals

ghci> (show . factorial) 5 

// equals

ghci> show . factorial $ 5 

It is the different between left —> right and right —> left. ⊙﹏⊙|||

Humanization

|> and & is better than .

because

ghci> sum (replicate 5 (max 6.7 8.9))

// equals

ghci> 8.9 & max 6.7 & replicate 5 & sum

// equals

ghci> 8.9 |> max 6.7 |> replicate 5 |> sum

// equals

ghci> (sum . replicate 5 . max 6.7) 8.9

// equals

ghci> sum . replicate 5 . max 6.7 $ 8.9

How to functional programming in object-oriented language?

please visit http://reactivex.io/

It support :

• Java: RxJava
• JavaScript: RxJS
• C#: Rx.NET
• C#(Unity): UniRx
• Scala: RxScala
• Clojure: RxClojure
• C++: RxCpp
• Lua: RxLua
• Ruby: Rx.rb
• Python: RxPY
• Go: RxGo
• Groovy: RxGroovy
• JRuby: RxJRuby
• Kotlin: RxKotlin
• Swift: RxSwift
• PHP: RxPHP
• Elixir: reaxive
• Dart: RxDart