PureScript by Example - 4. Recursion, Maps And Folds - 4.4 Recursion on Arrays - Solutions to Exercises 1-2

Recursion.purs

module Recursion where

-- 4.4 Recursion on Arrays of PureScript by Example

import Prelude
import Data.Array.Partial
import Partial.Unsafe

-- Exercise 1
isEven :: Int -> Boolean
isEven 0 = true
isEven 1 = false
isEven n = isEven (n - 2)

-- Exercise 2
numEven :: Array Int -> Int
numEven [] = 0
numEven arr =
  (if isEven (unsafePartial head arr) then 1 else 0) +
  numEven (unsafePartial tail arr)