Added eof parser

[cc1516.git] / src / yard.icl

diff --git a/src/yard.icl b/src/yard.icl
index 5460312..582ea1d 100644 (file)
--- a/src/yard.icl
+++ b/src/yard.icl
@@ -4,23 +4,29 @@ import StdTuple
 import StdClass
 import StdString
 import StdList
+import StdInt
+from Data.List import intersperse
+from Text import instance Text String, class Text(concat)
 import Data.Functor
 import Data.Either
 import Control.Monad
 import Control.Applicative
 from Data.Func import $
+import Data.Void
 
 instance toString Error where
        toString ParseError = "General parse error"
        toString (LexError e) = "Lexer error: " +++ e
-
-instance + Error where
-    (+) (Expected as) (Expected bs) = Expected (as++bs)
-    (+) _ r                         = r
+    toString (Unexpected e pos) = "Unexpected " +++ e +++ " at position " +++ (toString pos)
 
 runParser :: (Parser a b) [a] -> (Either Error b, [a])
 runParser (Parser f) i = f i
 
+instance + Error where
+    (+) ParseError r = r 
+    (+) r ParseError = r
+    (+) r _          = r
+ 
 instance Functor (Parser a) where
     fmap f m = liftM f m
 
@@ -38,12 +44,13 @@ instance Alternative (Parser a) where
     (<|>) p1 p2 = Parser \i -> case runParser p1 i of
         (Right r, rest) = (Right r, rest)
         (Left e1, rest) = case runParser p2 i of
+            (Left e2, rest)  = (Left $ e1+e2, rest)
             (Right r, rest) = (Right r, rest)
-            (Left e2, rest) = (Left (e1+e2), rest)
 
-<?> :: (Parser a b) String -> Parser a b
-<?> p e = Parser \i -> case runParser p i of
-    (Left e1, rest) = (Left (e1+(Expected [e])), rest)
+//Try the parser, if it fails decorate the error with Expected of the given String and position
+(<?>) :: (Parser a b) (String, Int) -> Parser a b
+(<?>) p (e,pos) = Parser \i -> case runParser p i of
+    (Left e1, rest) = (Left $ e1 + Unexpected e pos, rest)
     (Right r, rest) = (Right r, rest)
 
 fail :: Parser a b
@@ -54,11 +61,24 @@ top = Parser \i -> case i of
     []      = (Left ParseError, [])
     [x:xs]  = (Right x, xs)
 
+peek :: Parser a a
+peek = Parser \i -> case i of
+    []      = (Left ParseError, [])
+    [x:xs]  = (Right x, [x:xs])
+
+eof :: Parser a Void
+eof = Parser \i -> case i of 
+    []      = (Right Void, [])
+    _       = (Left ParseError, i)
+
 satisfy :: (a -> Bool) -> Parser a a
 satisfy f = top >>= \r -> if (f r) (return r) fail
 
+check :: (a -> Bool) -> Parser a a
+check f = peek >>= \r -> if (f r) (return r) fail
+
 item :: a -> Parser a a | Eq a
 item a  = satisfy ((==)a)
 
 list :: [a] -> Parser a [a] | Eq a
-list as = mapM item as
+list as = mapM item as
\ No newline at end of file