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.Foldable
  import Text.Printf
  
  -- | The prefix of a name.  This implementation uses a case expression.
  prefixc :: String -> String
  prefixc name
      | 0 < size && size <= 3 = name
      | otherwise =
          case size of
              0 -> ['\0']
              _ -> [name !! 0]
    where
      size = length name
  
  -- | The prefix of a name.  This implementation does not use a case expression.
  prefixg :: String -> String
  prefixg name
      | size == 0 = ['\0']
      | size <= 3 = name
      | otherwise = [name !! 0]
    where
      size = length name
  
  -- | The prefix of a person's name.
  main = do
      let name =
              [ "Albrecht Dürer"
              , "Andrea Mantegna"
              , "Donatello"
              , ""
              , "Giovanni Bellini"
              , "Jan van Eyck"
              , "Jo"
              , "Leonardo da Vinci"
              , "Lorenzo Ghiberti"
              , "Michelangelo"
              , "Raphael"
              , "Sandro Botticelli"
              , "Sue"
              , "T"
              ]
      for_ name $ \x -> do
          let pre = prefixc x
          printf "%s -> %s, %s\n" x pre $ show (pre == prefixg x)
  