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-rw-r--r--src/unlambda.hs30
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diff --git a/src/unlambda.hs b/src/unlambda.hs
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+++ b/src/unlambda.hs
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+
+import System.Environment( getArgs )
+import Control.Exception( ErrorCall(..), Handler(..), catches )
+import Unlambda.Parser
+import Unlambda.Interpreter
+
+
+
+
+usageString :: String
+usageString = "Usage: unlambda <program file>"
+
+
+
+program :: IO ()
+program = do
+ args <- getArgs
+ fileContents <- if (length args /= 1)
+ then error usageString
+ else readFile (head args)
+
+ case (parseUnlambda fileContents) of
+ Left x -> putStrLn (show x)
+ Right x -> unlambda x >>= putStrLn . show
+
+
+
+main = catches program
+ [ Handler ((\e -> putStrLn . show $ e) :: ErrorCall -> IO ()) ]
+