Calculates Chinese zodiac sign for a given year

Zodiac.hs

import System.Console.GetOpt (ArgOrder(..), getOpt)
import System.Environment (getArgs)

offset = (flip mod) 12

animal 4  = "Rat"
animal 5  = "Ox"
animal 6  = "Tiger"
animal 7  = "Rabbit"
animal 8  = "Dragon"
animal 9  = "Snake"
animal 10 = "Horse"
animal 11 = "Sheep"
animal 0  = "Monkey"
animal 1  = "Rooster"
animal 2  = "Dog"
animal 3  = "Pig"

parseArgs = getOpt RequireOrder []

main = do
    argv <- getArgs
    let year = case parseArgs argv of
                 ([], year:_, []) -> read year :: Int
    putStrLn $ animal $ offset year