change.ls

fit = (coins, amt)-->
  maximum filter (<= amt), coins

fit-sterling = fit [1 2 5 10 20 50 100 200]

change = (fit, amt)-->
  | amt is 0 => []
  | otherwise => let coin = fit amt
    [coin] ++ change fit, (amt - coin)

names =
  1: 'penny'
  2: 'tuppence'
  5: 'fivepence'
  10: 'ten pence'
  20: 'twenty pence'
  50: 'fifty pence'
  100: 'quid'
  200: 'two quid'

count-by (names.), change fit-sterling, 16564