printExpr (ExprOp a x b) = "(" ++ printExpr a ++ " " ++ x ++ " " ++ printExpr b ++ ")"
printExpr (ExprOp a x b) = "(" ++ printExpr a ++ " " ++ x ++ " " ++ printExpr b ++ ")"
printExpr (ExprOp a x b) = "(" ++ printExpr a ++ " " ++ x ++ " " ++ printExpr b ++ ")"