tax Credit A and B, Haskell

taxcredits.hs

#!stack
-- stack --resolver lts-15.12 script

data Person = Person { pname :: String, children :: [Person] }
a = Person "Alice" []
b = Person "Bob"   []
c = Person "Carol" [a, b]

data TaxCredit = TaxCredit { tcname :: String, rate :: Person -> Int }

taxCreditB = TaxCredit "Tax Credit B" (\person -> 100)

taxCreditA = taxCreditB { tcname = "Tax Credit A"
                        , rate = \person -> let usualresult = (rate taxCreditB) person
                                            in  if   length (children person) == 2
                                                then usualresult `div` 2
                                                else usualresult }

main = do
  mapM_ putStrLn [ unwords [ pname p ++ ":\t", tcname tc, "=", show ((rate tc) p) ]
                 | tc <- [taxCreditB, taxCreditA]
                 , p  <- [a, b, c] ]

{-
   20200612-22:37:23 mengwong@venice4:~/tmp/python/taxc% stack taxc.hs
   Alice:   Tax Credit B = 100
   Bob:     Tax Credit B = 100
   Carol:   Tax Credit B = 100
   Alice:   Tax Credit A = 100
   Bob:     Tax Credit A = 100
   Carol:   Tax Credit A = 50
-}