Unix-like piping DSL for purescript

console

> import Fun
> import Data.Array
> 20 >> fibs |> filter isEven |> length
7

Fun.purs

module Fun where

import Data.Array (map, filter, (..))

-- Given an argument `a` applies the function `f`
(>>) :: forall a b. a -> (a -> b) -> b
(>>) a f = f a
infix 1 >>

-- Given functions `f` and `g`, composes to yield `g` of `f`
(|>) :: forall a b c. (a -> b) -> (b -> c) -> (a -> c)
(|>) f g a = g $ f a
infixr 2 |>
  
-- Calculates the nth fibonacci number
fib :: Number -> Number
fib 0 = 1
fib 1 = 1
fib n = fib (n - 1) + fib (n - 2)

-- Returns the first n fibonacci numbers
fibs :: Number -> [Number]
fibs n = 0..n >> map fib

-- Determines if a given number is even
isEven :: Number -> Boolean
isEven n = n % 2 == 0

How many of the first 20 Fibonacci numbers are even? Redirect 20 into the pipeline of functions!