src/yard.icl

   1 implementation module yard
   2
   3 import StdTuple
   4 import StdClass
   5 import StdString
   6 import StdList
   7 import StdInt
   8 from Data.List import intersperse
   9 from Text import instance Text String, class Text(concat)
  10 import Data.Functor
  11 import Data.Either
  12 import Control.Monad
  13 import Control.Applicative
  14 from Data.Func import $
  15
  16 instance toString Error where
  17         toString ParseError = "General parse error"
  18         toString (LexError e) = "Lexer error: " +++ e
  19     toString (Unexpected e pos) = "Unexpected " +++ e +++ " at position " +++ (toString pos)
  20
  21 runParser :: (Parser a b) [a] -> (Either Error b, [a])
  22 runParser (Parser f) i = f i
  23
  24 instance + Error where
  25     (+) ParseError r = r
  26     (+) r ParseError = r
  27     (+) r _          = r
  28
  29 instance Functor (Parser a) where
  30     fmap f m = liftM f m
  31
  32 instance Applicative (Parser a) where
  33     pure a      = Parser \i -> (Right a, i)
  34     (<*>) sf p  = ap sf p
  35
  36 instance Monad (Parser a) where
  37     bind p f    = Parser \i -> case runParser p i of
  38         (Right r, rest) = runParser (f r) rest
  39         (Left e, rest)  = (Left e, rest)
  40
  41 instance Alternative (Parser a) where
  42     empty       = Parser \i -> (Left ParseError, i)
  43     (<|>) p1 p2 = Parser \i -> case runParser p1 i of
  44         (Right r, rest) = (Right r, rest)
  45         (Left e1, rest) = case runParser p2 i of
  46             (Left e2, rest)  = (Left $ e1+e2, rest)
  47             (Right r, rest) = (Right r, rest)
  48
  49 //Try the parser, if it fails decorate the error with Expected of the given String and position
  50 (<?>) :: (Parser a b) (String, Int) -> Parser a b
  51 (<?>) p (e,pos) = Parser \i -> case runParser p i of
  52     (Left e1, rest) = (Left $ e1 + Unexpected e pos, rest)
  53     (Right r, rest) = (Right r, rest)
  54
  55 fail :: Parser a b
  56 fail = empty
  57
  58 top :: Parser a a
  59 top = Parser \i -> case i of
  60     []      = (Left ParseError, [])
  61     [x:xs]  = (Right x, xs)
  62
  63 satisfy :: (a -> Bool) -> Parser a a
  64 satisfy f = top >>= \r -> if (f r) (return r) fail
  65
  66 item :: a -> Parser a a | Eq a
  67 item a  = satisfy ((==)a)
  68
  69 list :: [a] -> Parser a [a] | Eq a
  70 list as = mapM item as