X-Git-Url: https://git.martlubbers.net/?a=blobdiff_plain;f=src%2Fyard.icl;h=b5e3c61f885002285eab6d8c6fc38aa6bd189385;hb=96be5e0151b236a425025cf96e8dade73ee74fcf;hp=2f3c90ac6b3b7bbeebce21036777a4712a302f7d;hpb=b4636110ab65f233ed40d4390b62c7799df3c949;p=cc1516.git

diff --git a/src/yard.icl b/src/yard.icl
index 2f3c90a..b5e3c61 100644
--- a/src/yard.icl
+++ b/src/yard.icl
@@ -3,6 +3,10 @@ implementation module yard
 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
@@ -12,10 +16,16 @@ from Data.Func import $
 instance toString Error where
 	toString ParseError = "General parse error"
 	toString (LexError e) = "Lexer error: " +++ e
+    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
 
@@ -32,7 +42,15 @@ instance Alternative (Parser a) where
     empty       = Parser \i -> (Left ParseError, i)
     (<|>) p1 p2 = Parser \i -> case runParser p1 i of
         (Right r, rest) = (Right r, rest)
-        (Left _, rest)  = runParser p2 i
+        (Left e1, rest) = case runParser p2 i of
+            (Left e2, rest)  = (Left $ e1+e2, rest)
+            (Right r, rest) = (Right r, 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
 fail = empty