never executed always true always false

    1 module Main where
    2 
    3 import LI11718
    4 import qualified Tarefa3_2017li1g183 as T3
    5 
    6 import System.Environment
    7 import Text.Read
    8 
    9 main = do
   10     args <- getArgs
   11     case args of
   12         ["movimenta"] -> do
   13             str <- getContents
   14             let params = readMaybe str
   15             case params of
   16                 Nothing -> error "parâmetros inválidos"
   17                 Just (mapa,tempo,carro) -> print $ T3.movimenta mapa tempo carro
   18         ["testes"] -> print $ T3.testesT3
   19         otherwise -> error "RunT3 argumentos inválidos"