From d355a5db8a95bc9fc79a801327bb45c1ed885783 Mon Sep 17 00:00:00 2001
From: Ivy <adrisolgo7373@gmail.com>
Date: Sat, 30 Jan 2021 14:55:22 +0100
Subject: [PATCH] Added cons expression

---
 src/Evaluator.hs |  3 ++-
 src/ExprType.hs  |  1 +
 src/Lexer.hs     |  2 +-
 src/Parser.hs    | 16 +++++++++++++++-
 4 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/Evaluator.hs b/src/Evaluator.hs
index 22a31a1..7bb0da5 100644
--- a/src/Evaluator.hs
+++ b/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
diff --git a/src/ExprType.hs b/src/ExprType.hs
index 704c06d..06be2a6 100644
--- a/src/ExprType.hs
+++ b/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
diff --git a/src/Lexer.hs b/src/Lexer.hs
index 5a60f82..beff3b5 100644
--- a/src/Lexer.hs
+++ b/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
diff --git a/src/Parser.hs b/src/Parser.hs
index 28a84fc..9eb69dc 100644
--- a/src/Parser.hs
+++ b/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