add boolean type and constants

ast.hs

@@ -20,6 +20,7 @@ data AST = Add AST AST
 		 | IfExpr AST AST AST
 		 | TupleConst [AST]
 		 | ListConst [AST]
+		 | BoolConst Bool
 		 | StrConst String
 		 | IntConst Integer
 		 deriving (Show, Eq)

interp.hs

@@ -21,6 +21,7 @@ instance Eq BIF where a == b = False
 data Value = IntV Integer
 		   | StrV String
 		   | UnitV
+		   | BoolV Bool
 		   | StreamV Int
 		   | TupleV [Value]
 		   | ListV [Value]
@@ -99,6 +100,7 @@ eval :: AST -> InterpState Value
 
 eval (IntConst i) = return $ IntV i
 eval (StrConst s) = return $ StrV s
+eval (BoolConst b) = return $ BoolV b
 
 eval UnitConst = return UnitV
 

parser.hs

@@ -137,6 +137,8 @@ ifExpr = do
 	e <- exprparser
 	return $ IfExpr cond t e
 
+bool = fmap BoolConst $ (symbol "true" >> return True) <|> (symbol "false" >> return False)
+
 expr' = try block
 	 <|> try funDef
 	 <|> try call
@@ -145,6 +147,7 @@ expr' = try block
 	 <|> parens exprparser
 	 <|> listSeq exprparser ListConst
 	 <|> try ifExpr
+	 <|> bool
 	 <|> fmap Var identifier
 	 <|> fmap StrConst stringLiteral
 	 <|> fmap IntConst integer