Added cons expression

src/Evaluator.hs

@@ -14,10 +14,11 @@ base = M.fromList [
   ]
 
 eval :: Env -> Expr -> (Env, Expr)
-eval env (IntE x)      = (env, IntE x)
+eval env i@(IntE x)      = (env, i)
 eval env (VarE v)      = (M.insert v nExpr nEnv, nExpr)
   where (nEnv, nExpr) = eval env $ env M.! v
 eval env (SetE v expr) = (M.insert v expr env, NilE)
+eval env c@(ConsE _ _) = (env, c)
 eval env NilE          = (env, NilE)
 
 --apply :: Proc -> Args -> Expr

src/ExprType.hs

@@ -4,6 +4,7 @@ data Expr = IntE Integer
           | VarE String
           | ProcedureE String [Expr]
           | SetE String Expr
+          | ConsE Expr Expr
           | NilE deriving (Show)
 
 -- instance Show Expr where

src/Lexer.hs

@@ -29,5 +29,5 @@ rightParenT = char ')' >> return RightParenT
 
 symbolT :: GenParser Char st Token
 symbolT = do
-    var <- map toLower <$> many1 (letter <|> oneOf "+-*/!|@#$~%&/=<>")
+    var <- map toLower <$> many1 (letter <|> oneOf "+-*/\\!|@#$~%&/=<>")
     return $ SymbolT var

src/Parser.hs

@@ -20,7 +20,7 @@ expressionFromTokensEOF = do
 
 expressionFromTokens :: GenParser Token st Expr
 expressionFromTokens = do
-  expr <- intE <|> try setE <|> try nilE <|> varE <|> procedureE
+  expr <- intE <|> try setE <|> try nilE <|> try consE <|> varE <|> procedureE
   return expr
 
 intE :: GenParser Token st Expr
@@ -36,6 +36,15 @@ procedureE = do
   _ <- parseRightParenT
   return $ ProcedureE p args
 
+consE :: GenParser Token st Expr
+consE = do
+  _ <- parseLeftParenT
+  _ <- parseConsT
+  expr1 <- expressionFromTokens
+  expr2 <- expressionFromTokens
+  _ <- parseRightParenT
+  return $ ConsE expr1 expr2
+
 varE :: GenParser Token st Expr
 varE = do
   (SymbolT var) <- parseSymbolT
@@ -78,6 +87,11 @@ parseNilT = satisfyT isNilT
   where isNilT (SymbolT "nil") = True
         isNilT _               = False
 
+parseConsT :: GenParser Token st Token
+parseConsT = satisfyT isConsT
+  where isConsT (SymbolT "cons") = True
+        isConsT _               = False
+
 parseSymbolT :: GenParser Token st Token
 parseSymbolT = satisfyT isSymbolT
   where isSymbolT (SymbolT _) = True