+peek :: Parser a a
+peek = Parser \i -> case i of
+ [] = (Left $ Error "", [])
+ [x:xs] = (Right x, [x:xs])
+
+//runs the left parser until the right parser succeeds. Returns the result of the left parser
+//Note: if the right parser consumes input then this input is lost!
+//If the left parser fails before the right parser succeeds the whole parser fails
+(until) infix 2 :: (Parser a b) (Parser a c) -> Parser a [b]
+(until) p guard = try $ until` p guard []
+ where
+ until` :: (Parser a b) (Parser a c) [b] -> Parser a [b]
+ until` p guard acc = Parser \i -> case runParser guard i of
+ (Right _, rest) = (Right acc, rest)
+ (Left _, _) = case runParser p i of
+ (Right r, rest) = runParser (until` p guard [r:acc]) rest
+ (Left e, _) = (Left e, i)
+ try :: (Parser a b) -> Parser a b
+ try p = Parser \i -> case runParser p i of
+ (Left e, _) = (Left e, i)
+ (Right r, rest) = (Right r, rest)
+
+
+eof :: Parser a Void
+eof = Parser \i -> case i of
+ [] = (Right Void, [])
+ _ = (Left $ Error "", i)
+