Now vars 'set!' and 'nil' are treated as symbols in the lexer

cherry-lisp.cabal

@@ -22,8 +22,7 @@ executable cherry
                        Parser,
                        TokenType,
                        Lexer,
-                       Evaluator,
-                       ParserUtils
+                       Evaluator
 
   build-depends:       base >= 4.7 && < 5,
                        containers,

src/Lexer.hs

@@ -1,7 +1,6 @@
 module Lexer where
 
 import Text.ParserCombinators.Parsec
-import ParserUtils
 import Data.Char
 import TokenType
 
@@ -13,7 +12,7 @@ parseTokens = do
     return tokns
 
 anyLispToken :: GenParser Char st Token
-anyLispToken = leftParenT <|> rightParenT <|> try nilT <|> try setT <|> varT <|> intT
+anyLispToken = leftParenT <|> rightParenT <|> symbolT <|> intT
 
 ------------------------------------------------------------
 
@@ -28,13 +27,7 @@ leftParenT = char '(' >> return LeftParenT
 rightParenT :: GenParser Char st Token
 rightParenT = char ')' >> return RightParenT
 
-setT :: GenParser Char st Token
-setT = caseInsensitiveString "set!" >> return SetT
-
-nilT :: GenParser Char st Token
-nilT = caseInsensitiveString "nil" >> return NilT
-
-varT :: GenParser Char st Token
-varT = do
+symbolT :: GenParser Char st Token
+symbolT = do
     var <- map toLower <$> many1 (letter <|> oneOf "+-*/!|@#$~%&/=<>")
-    return $ VarT var
+    return $ SymbolT var

src/Parser.hs

@@ -20,7 +20,7 @@ expressionFromTokensEOF = do
 
 expressionFromTokens :: GenParser Token st Expr
 expressionFromTokens = do
-  expr <- intE <|> try defineE <|> try nilE <|> varE <|> procedureE
+  expr <- intE <|> try setE <|> try nilE <|> varE <|> procedureE
   return expr
 
 intE :: GenParser Token st Expr
@@ -31,14 +31,14 @@ intE = do
 procedureE :: GenParser Token st Expr
 procedureE = do
   _ <- parseLeftParenT
-  (VarT p) <- parseVarT
+  (SymbolT p) <- parseSymbolT
   args <- many expressionFromTokens
   _ <- parseRightParenT
   return $ ProcedureE p args
 
 varE :: GenParser Token st Expr
 varE = do
-  (VarT var) <- parseVarT
+  (SymbolT var) <- parseSymbolT
   return $ VarE var
 
 nilE :: GenParser Token st Expr
@@ -46,11 +46,11 @@ nilE = do
   _ <- parseNilT
   return NilE
 
-defineE :: GenParser Token st Expr
-defineE = do
+setE :: GenParser Token st Expr
+setE = do
   _ <- parseLeftParenT
   _ <- parseSetT
-  (VarT var) <- parseVarT
+  (SymbolT var) <- parseSymbolT
   expr <- expressionFromTokens
   _ <- parseRightParenT
   return $ SetE var expr
@@ -69,15 +69,19 @@ parseRightParenT :: GenParser Token st Token
 parseRightParenT = satisfyT (== RightParenT)
 
 parseSetT :: GenParser Token st Token
-parseSetT = satisfyT (== SetT)
+parseSetT = satisfyT isSetT
+  where isSetT (SymbolT "set!") = True
+        isSetT _               = False
 
 parseNilT :: GenParser Token st Token
-parseNilT = satisfyT (== NilT)
+parseNilT = satisfyT isNilT
+  where isNilT (SymbolT "nil") = True
+        isNilT _               = False
 
-parseVarT :: GenParser Token st Token
-parseVarT = satisfyT isVarT
-  where isVarT (VarT _) = True
-        isVarT _        = False
+parseSymbolT :: GenParser Token st Token
+parseSymbolT = satisfyT isSymbolT
+  where isSymbolT (SymbolT _) = True
+        isSymbolT _        = False
 
 parseIntT :: GenParser Token st Token
 parseIntT = satisfyT isIntT

src/ParserUtils.hs

@@ -1,3 +1,4 @@
+-- UNUSED
 module ParserUtils where
 
 import Text.ParserCombinators.Parsec

src/TokenType.hs

@@ -2,8 +2,6 @@ module TokenType where
 
 data Token = LeftParenT
            | RightParenT
-           | SetT
-           | VarT String
+           | SymbolT String
            | IntT Integer
-           | NilT
            deriving (Show, Eq)