Straightforward While lexer, parser and interpreter

1 files changed, 84 insertions, 0 deletions

diff --git a/paper/While/Yard.icl b/paper/While/Yard.icl
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+implementation module Yard
+
+import StdTuple
+import StdClass
+import StdString
+import StdList
+import StdInt
+
+import Common
+
+concat :: ([String] -> String)
+concat = foldl (+++) ""
+
+intersperse :: !a ![a] -> [a]
+intersperse i []      = []
+intersperse i [x]     = [x]
+intersperse i [x:xs]  = [x,i:intersperse i xs]
+
+runParser :: (Parser a b) [a] -> (Either Error b, [a])
+runParser (Parser f) i = f i
+ 
+instance Functor (Parser a) where
+	(<$>) f m = m >>= \x -> pure (f x)
+
+instance Applicative (Parser a) where
+	pure a	  = Parser \i -> (Right a, i)
+	(<*>) sf p  = sf >>= \sf` -> p >>= \p` -> pure (sf` p`)
+
+instance Monad (Parser a) where
+	(>>=) p f	= Parser \i -> case runParser p i of
+		(Right r, rest) = runParser (f r) rest
+		(Left e, _)	 = (Left e, i)
+
+instance Alternative (Parser a) where
+	empty	   = Parser \i -> (Left $ GenericError "" , i)
+	(<|>) p1 p2 = Parser \i -> case runParser p1 i of
+		(Right r, rest) = (Right r, rest)
+		(Left e1, rest) = case runParser p2 i of
+			(Left e2, rest)  = (Left e2, i)
+			(Right r, rest)  = (Right r, rest)
+
+(<?>) :: (Parser a b) Error -> Parser a b
+(<?>) p e = Parser \i -> case runParser p i of
+	(Left e1, rest) = (Left e, rest)
+	(Right r, rest) = (Right r, rest)
+
+fail :: Parser a b
+fail = empty
+
+top :: Parser a a
+top = Parser \i -> case i of
+	[]	  = (Left $ GenericError "", [])
+	[x:xs]  = (Right x, xs)
+
+peek :: Parser a a
+peek = Parser \i -> case i of
+	[]	  = (Left $ GenericError "", [])
+	[x:xs]  = (Right x, [x:xs])
+
+(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)
+
+satisfy :: (a -> Bool) -> Parser a a
+satisfy f = top >>= \r -> if (f r) (pure r) fail
+
+check :: (a -> Bool) -> Parser a a
+check f = peek >>= \r -> if (f r) (pure r) fail
+
+item :: a -> Parser a a | == a
+item a  = satisfy ((==)a)
+
+list :: [a] -> Parser a [a] | == a
+list as = mapM item as