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+{-# LANGUAGE TemplateHaskell #-}
+
+-- Used by QuasiQuote. Example taken from the GHC documentation.
+module QuasiExpr where
+
+import Language.Haskell.TH
+import Language.Haskell.TH.Quote
+
+data Expr = IntExpr Integer
+ | AntiIntExpr String
+ | BinopExpr BinOp Expr Expr
+ | AntiExpr String
+ deriving Show
+
+data BinOp = AddOp
+ | SubOp
+ | MulOp
+ | DivOp
+ deriving Show
+
+eval :: Expr -> Integer
+eval (IntExpr n) = n
+eval (BinopExpr op x y) = (opToFun op) (eval x) (eval y)
+ where
+ opToFun AddOp = (+)
+ opToFun SubOp = (-)
+ opToFun MulOp = (*)
+ opToFun DivOp = div
+
+expr = QuasiQuoter parseExprExp undefined undefined undefined
+
+-- cheating...
+parseExprExp :: String -> Q Exp
+parseExprExp _ = [| BinopExpr AddOp (IntExpr 1) (IntExpr 2) |]