content: -- ZECKENDORF NUMBERS --------------------------------------------------------
  
  -- zeckendorf :: Int -> String
  on zeckendorf(n)
      script f
          on |λ|(n, x)
              if n < x then
                  [n, 0]
              else
                  [n - x, 1]
              end if
          end |λ|
      end script
  
      if n = 0 then
          {0} as string
      else
          item 2 of mapAccumL(f, n, |reverse|(just of tailMay(fibUntil(n)))) as string
      end if
  end zeckendorf
  
  -- fibUntil :: Int -> [Int]
  on fibUntil(n)
      set xs to {}
      set limit to n
  
      script atLimit
          property ceiling : limit
          on |λ|(x)
              (item 2 of x) > (atLimit's ceiling)
          end |λ|
      end script
  
      script nextPair
          property series : xs
          on |λ|([a, b])
              set nextPair's series to nextPair's series & b
              [b, a + b]
          end |λ|
      end script
  
      |until|(atLimit, nextPair, {0, 1})
      return nextPair's series
  end fibUntil
  
  -- TEST ----------------------------------------------------------------------
  on run
  
      intercalate(linefeed, ¬
          map(zeckendorf, enumFromTo(0, 20)))
  
  end run
  
  -- GENERIC FUNCTIONS ---------------------------------------------------------
  
  -- enumFromTo :: Int -> Int -> [Int]
  on enumFromTo(m, n)
      if m > n then
          set d to -1
      else
          set d to 1
      end if
      set lst to {}
      repeat with i from m to n by d
          set end of lst to i
      end repeat
      return lst
  end enumFromTo
  
  -- foldl :: (a -> b -> a) -> a -> [b] -> a
  on foldl(f, startValue, xs)
      tell mReturn(f)
          set v to startValue
          set lng to length of xs
          repeat with i from 1 to lng
              set v to |λ|(v, item i of xs, i, xs)
          end repeat
          return v
      end tell
  end foldl
  
  -- 'The mapAccumL function behaves like a combination of map and foldl;
  -- it applies a function to each element of a list, passing an
  -- accumulating parameter from left to right, and returning a final
  -- value of this accumulator together with the new list.' (see Hoogle)
  
  -- mapAccumL :: (acc -> x -> (acc, y)) -> acc -> [x] -> (acc, [y])
  on mapAccumL(f, acc, xs)
      script
          on |λ|(a, x)
              tell mReturn(f) to set pair to |λ|(item 1 of a, x)
              [item 1 of pair, (item 2 of a) & item 2 of pair]
          end |λ|
      end script
  
      foldl(result, [acc, []], xs)
  end mapAccumL
  
  -- map :: (a -> b) -> [a] -> [b]
  on map(f, xs)
      tell mReturn(f)
          set lng to length of xs
          set lst to {}
          repeat with i from 1 to lng
              set end of lst to |λ|(item i of xs, i, xs)
          end repeat
          return lst
      end tell
  end map
  
  -- Lift 2nd class handler function into 1st class script wrapper
  -- mReturn :: Handler -> Script
  on mReturn(f)
      if class of f is script then
          f
      else
          script
              property |λ| : f
          end script
      end if
  end mReturn
  
  -- intercalate :: Text -> [Text] -> Text
  on intercalate(strText, lstText)
      set {dlm, my text item delimiters} to {my text item delimiters, strText}
      set strJoined to lstText as text
      set my text item delimiters to dlm
      return strJoined
  end intercalate
  
  -- reverse :: [a] -> [a]
  on |reverse|(xs)
      if class of xs is text then
          (reverse of characters of xs) as text
      else
          reverse of xs
      end if
  end |reverse|
  
  -- tailMay :: [a] -> Maybe [a]
  on tailMay(xs)
      if length of xs > 1 then
          {nothing:false, just:items 2 thru -1 of xs}
      else
          {nothing:true}
      end if
  end tailMay
  
  -- until :: (a -> Bool) -> (a -> a) -> a -> a
  on |until|(p, f, x)
      set mp to mReturn(p)
      set v to x
  
      tell mReturn(f)
          repeat until mp's |λ|(v)
              set v to |λ|(v)
          end repeat
      end tell
      return v
  end |until|
  