Added quoted expressions

src/Evaluator.hs

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

src/ExprType.hs

@@ -5,6 +5,7 @@ data Expr = IntE Integer
           | ProcedureE String [Expr]
           | SetE String Expr
           | ConsE Expr Expr
+          | QuotedE Expr
           | NilE deriving (Show)
 
 -- instance Show Expr where

src/Lexer.hs

@@ -12,7 +12,7 @@ parseTokens = do
     return tokns
 
 anyLispToken :: GenParser Char st Token
-anyLispToken = leftParenT <|> rightParenT <|> symbolT <|> intT
+anyLispToken = leftParenT <|> rightParenT <|> apostropheT <|> symbolT <|> intT
 
 ------------------------------------------------------------
 
@@ -24,6 +24,9 @@ intT = do
 leftParenT :: GenParser Char st Token
 leftParenT = char '(' >> return LeftParenT
 
+apostropheT :: GenParser Char st Token
+apostropheT = char '\'' >> return ApostropheT
+
 rightParenT :: GenParser Char st Token
 rightParenT = char ')' >> return RightParenT
 

src/Parser.hs

@@ -20,7 +20,7 @@ expressionFromTokensEOF = do
 
 expressionFromTokens :: GenParser Token st Expr
 expressionFromTokens = do
-  expr <- intE <|> try setE <|> try nilE <|> try consE <|> varE <|> procedureE
+  expr <- intE <|> quotedE <|> try setE <|> try nilE <|> try consE <|> varE <|> procedureE
   return expr
 
 intE :: GenParser Token st Expr
@@ -28,6 +28,12 @@ intE = do
     (IntT num) <- parseIntT
     return $ IntE num
 
+quotedE :: GenParser Token st Expr
+quotedE = do
+  _ <- parseApostropheT
+  expr <- expressionFromTokens
+  return $ QuotedE expr
+
 procedureE :: GenParser Token st Expr
 procedureE = do
   _ <- parseLeftParenT
@@ -77,6 +83,9 @@ parseLeftParenT = satisfyT (== LeftParenT)
 parseRightParenT :: GenParser Token st Token
 parseRightParenT = satisfyT (== RightParenT)
 
+parseApostropheT :: GenParser Token st Token
+parseApostropheT = satisfyT (== ApostropheT)
+
 parseSetT :: GenParser Token st Token
 parseSetT = satisfyT isSetT
   where isSetT (SymbolT "set!") = True

src/TokenType.hs

@@ -3,5 +3,6 @@ module TokenType where
 data Token = LeftParenT
            | RightParenT
            | SymbolT String
+           | ApostropheT
            | IntT Integer
            deriving (Show, Eq)