content: -- PERFECT NUMBERS -----------------------------------------------------------
  
  -- perfect :: integer -> bool
  on perfect(n)
  
      -- isFactor :: integer -> bool
      script isFactor
          on |λ|(x)
              n mod x = 0
          end |λ|
      end script
  
      -- quotient :: number -> number
      script quotient
          on |λ|(x)
              n / x
          end |λ|
      end script
  
      -- sum :: number -> number -> number
      script sum
          on |λ|(a, b)
              a + b
          end |λ|
      end script
  
      -- Integer factors of n below the square root
      set lows to filter(isFactor, enumFromTo(1, (n ^ (1 / 2)) as integer))
  
      -- low and high factors (quotients of low factors) tested for perfection
      (n > 1) and (foldl(sum, 0, (lows & map(quotient, lows))) / 2 = n)
  end perfect
  
  
  -- TEST ----------------------------------------------------------------------
  on run
  
      filter(perfect, enumFromTo(1, 10000))
  
      --> {6, 28, 496, 8128}
  
  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
  
  -- filter :: (a -> Bool) -> [a] -> [a]
  on filter(f, xs)
      tell mReturn(f)
          set lst to {}
          set lng to length of xs
          repeat with i from 1 to lng
              set v to item i of xs
              if |λ|(v, i, xs) then set end of lst to v
          end repeat
          return lst
      end tell
  end filter
  
  -- 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
  
  -- 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
  