lambda

diff --git a/lambda.hs b/lambda.hs
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+++ b/lambda.hs
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+import Data.Text as T
+import Data.Attoparsec.Text
+import Control.Applicative
+
+data Term = Var String | Lambda Term Term | App Term Term
+
+instance Show Term where
+  show (Var x) = x
+  show (Lambda (Var x) t) = "\\" ++ x ++ "." ++ show t
+  show (App t r) = "(" ++ show t ++ " " ++ show r ++ ")"
+
+--instance Read Term where
+tRead s = case parseOnly (parseTerm <* endOfInput) (T.pack s) of
+    (Right t) -> t
+    (Left e) -> error e
+
+parseVar :: Parser Term
+parseVar = do
+  x <- many1 letter
+  return $! Var x
+
+parseLambda :: Parser Term
+parseLambda = do
+  char '\\'
+  x <- parseVar
+  char '.'
+  t <- parseTerm
+  return $! Lambda x t
+
+
+parseApp :: Parser Term
+parseApp = do
+  char '('
+  t <- parseTerm
+  char ' '
+  r <- parseTerm
+  char '('
+  return $! App t r
+
+parseTerm :: Parser Term
+parseTerm = parseVar <|> parseLambda <|> parseApp