X-Git-Url: https://git.martlubbers.net/?a=blobdiff_plain;ds=sidebyside;f=src%2Fyard.icl;h=546031252484cb5b98a3c0f540c5b7623bfa94e7;hb=61fef22563cae53d4cf43680fe16703af4a1e822;hp=2f3c90ac6b3b7bbeebce21036777a4712a302f7d;hpb=b4636110ab65f233ed40d4390b62c7799df3c949;p=cc1516.git

diff --git a/src/yard.icl b/src/yard.icl
index 2f3c90a..5460312 100644
--- a/src/yard.icl
+++ b/src/yard.icl
@@ -3,6 +3,7 @@ implementation module yard
 import StdTuple
 import StdClass
 import StdString
+import StdList
 import Data.Functor
 import Data.Either
 import Control.Monad
@@ -13,6 +14,10 @@ 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
+
 runParser :: (Parser a b) [a] -> (Either Error b, [a])
 runParser (Parser f) i = f i
 
@@ -32,7 +37,14 @@ 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
+            (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)
+    (Right r, rest) = (Right r, rest)
 
 fail :: Parser a b
 fail = empty