content: --------------------------------------------------------------------------------
  -- MIT License
  --
  -- Copyright (C) 2024 Aaron Nguyen <mvngu [AT] gmx [DOT] com>
  --
  -- Permission is hereby granted, free of charge, to any person obtaining a copy
  -- of this software and associated documentation files (the "Software"), to deal
  -- in the Software without restriction, including without limitation the rights
  -- to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  -- copies of the Software, and to permit persons to whom the Software is
  -- furnished to do so, subject to the following conditions:
  --
  -- The above copyright notice and this permission notice shall be included in
  -- all copies or substantial portions of the Software.
  --
  -- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  -- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  -- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  -- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  -- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  -- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  -- SOFTWARE.
  --------------------------------------------------------------------------------
  
  import Text.Printf
  
  -- | Compose a function with itself n times.
  compose :: Int -> (a -> a) -> (a -> a)
  compose n f = foldr (\g acc -> acc . g) f functionList
    where
      functionList = replicate n f
  
  -- | Double a number.
  double :: Num a => a -> a
  double x = 2 * x
  
  -- | Compose a function with itself.
  main = do
      let [a, b, c, d] = [8, 3, 5, 2] :: [Integer]
      let [j, k, m, n] = [-1, 0, 1, 2] :: [Int]
      let aa = (compose k double) a
      let ab = double a
      let ba = (compose m double) b
      let bb = double . double $ b
      let ca = (compose n double) c
      let cb = double . double . double $ c
      let da = (compose j double) d
      let db = double d
      let testa = aa == ab
      let testb = ba == bb
      let testc = ca == cb
      let testd = da == db
      printf "%d -> %d, %s\n" a aa $ show testa
      printf "%d -> %d, %s\n" b ba $ show testb
      printf "%d -> %d, %s\n" c ca $ show testc
      printf "%d -> %d, %s\n" d da $ show testd
  