Implement AbstractSyntaxTree

app/AbstractSyntaxTree.hs

@@ -0,0 +1,36 @@
+module AbstractSyntaxTree where
+
+import qualified Parser
+
+type AST = Node
+
+data Node = Operation Opcode Node Node
+          | Scalar Int
+          deriving Show
+
+data Opcode = Add
+            | Sub
+            | Mult
+            | Div
+            deriving Show
+
+createAST :: Parser.CST -> AST
+createAST = simplifyExpr
+
+simplifyExpr :: Parser.Expr -> Node
+simplifyExpr expr = case expr of
+    Parser.Add term expr2 -> Operation Add (simplifyTerm term) (simplifyExpr expr2)
+    Parser.Sub term expr2 -> Operation Sub (simplifyTerm term) (simplifyExpr expr2)
+    Parser.ETerm term -> simplifyTerm term
+
+simplifyTerm :: Parser.Term -> Node
+simplifyTerm term = case term of
+    Parser.Mult factor term2 -> Operation Mult (simplifyFactor factor) (simplifyTerm term2)
+    Parser.Div  factor term2 -> Operation Div  (simplifyFactor factor) (simplifyTerm term2)
+    Parser.TFactor factor -> simplifyFactor factor
+
+simplifyFactor :: Parser.Factor -> Node
+simplifyFactor factor = case factor of
+    Parser.Integer i -> Scalar i
+    Parser.Parantheses expr -> simplifyExpr expr
+    Parser.NegFactor  factor2 -> Operation Mult (Scalar (-1)) (simplifyFactor factor2)

app/Main.hs

@@ -2,8 +2,11 @@ module Main where
 
 import qualified Lexer
 import qualified Parser
+import qualified AbstractSyntaxTree as AST
 
 main :: IO ()
 main = do
   source <- readFile "arithmetic.txt"
-  putStr $ show (Parser.parse $ Lexer.lex source)
+  case Parser.parse $ Lexer.lex source of
+    Just source -> print $ AST.createAST source
+    _ -> putStr "Some error"