1 implementation module yard
9 import Control.Applicative
10 from Data.Func import $
12 instance toString Error where
13 toString ParseError = "General parse error"
14 toString (LexError e) = "Lexer error: " +++ e
16 runParser :: (Parser a b) [a] -> (Either Error b, [a])
17 runParser (Parser f) i = f i
19 instance Functor (Parser a) where
22 instance Applicative (Parser a) where
23 pure a = Parser \i -> (Right a, i)
26 instance Monad (Parser a) where
27 bind p f = Parser \i -> case runParser p i of
28 (Right r, rest) = runParser (f r) rest
29 (Left e, rest) = (Left e, rest)
31 instance Alternative (Parser a) where
32 empty = Parser \i -> (Left ParseError, i)
33 (<|>) p1 p2 = Parser \i -> case runParser p1 i of
34 (Right r, rest) = (Right r, rest)
35 (Left _, rest) = runParser p2 i
41 top = Parser \i -> case i of
42 [] = (Left ParseError, [])
43 [x:xs] = (Right x, xs)
45 satisfy :: (a -> Bool) -> Parser a a
46 satisfy f = top >>= \r -> if (f r) (return r) fail
48 item :: a -> Parser a a | Eq a
49 item a = satisfy ((==)a)
51 list :: [a] -> Parser a [a] | Eq a
52 list as = mapM item as