Haskell-book/06/src/Main.purs


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module Main where

import Prelude
import Control.Monad.Eff (Eff)
import Control.Monad.Eff.Console (CONSOLE, log)

data DayOfWeek =
    Mon | Tue | Weds | Thu | Fri | Sat | Sun

data Date =
    Date DayOfWeek Int

instance eqDayOfWeek :: Eq DayOfWeek where
    eq Mon Mon = true
    eq Tue Tue = true
    eq Weds Weds = true
    eq Thu Thu = true
    eq Fri Fri = true
    eq Sat Sat = true
    eq Sun Sun = true
    eq _ _ = false

instance eqDate :: Eq Date where
    eq (Date weekday dayOfMonth)
       (Date weekday' dayOfMonth') =
        weekday == weekday' && dayOfMonth == dayOfMonth'

main :: forall e. Eff (console :: CONSOLE | e) Unit
main = do
  log "Hello sailor!"