content: --------------------------------------------------------------------------------
  -- MIT License
  --
  -- Copyright (C) 2023 Duck McSouls <quacksouls [AT] gmail [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
  
  -- | The body mass index (BMI).  Weight is in kilograms and height is
  -- in metres.
  bmi :: Double -> Double -> Double
  bmi weight height = weight / (height ** 2)
  
  -- | The weight status of an adult 20 years or older, based on their BMI.
  weightStatus :: Double -> String
  weightStatus bm
      | bm < 18.5 = "underweight"
      | 18.5 <= bm && bm <= 24.9 = "healthy weight"
      | 25.0 <= bm && bm <= 29.9 = "overweight"
      | bm >= 30.0 = "obese"
      | otherwise = "unknown BMI or weight status"
  
  -- | Body mass index.
  main = do
      putStrLn "Enter your weight in kilograms."
      weight <- getLine
      putStrLn "Enter your height in metres."
      height <- getLine
      let w = read weight :: Double
      let h = read height :: Double
      printf "Your BMI: %f\n" $ bmi w h
      printf "Weight status: %s\n" $ weightStatus $ bmi w h
  