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 Data.Char
  import Data.Foldable
  import Text.Printf
  
  -- | The first vowel in a name.
  firstVowel :: String -> Char
  firstVowel str =
      case (vowel str) of
          []    -> '\0'
          (x:_) -> x
  
  -- | All vowels in a name.
  vowel :: String -> String
  vowel str = [s | s <- str, (toLower s) `elem` "aeiou"]
  
  -- | The first vowel in a name.
  main = do
      let name =
              [ "Albrecht Dürer"
              , "Andrea Mantegna"
              , "Brynn Ng"
              , "Donatello"
              , "Giovanni Bellini"
              , "Gwynyth Symth"
              , "Jan van Eyck"
              , "Leonardo"
              , "Lorenzo Ghiberti"
              , "Michelangelo"
              , "Raphael"
              , "Sandro Botticelli"
              ]
      for_ name $ \x -> do
          printf "%s -> %c\n" x $ firstVowel x
  