From: pimjager Date: Tue, 1 Mar 2016 10:14:12 +0000 (+0100) Subject: Added until operator X-Git-Url: https://git.martlubbers.net/?a=commitdiff_plain;h=115831bb57dfb658d3b546de68b4ee755ac79df3;p=cc1516.git Added until operator --- diff --git a/src/yard.dcl b/src/yard.dcl index a029c4b..38ce368 100644 --- a/src/yard.dcl +++ b/src/yard.dcl @@ -25,6 +25,7 @@ top :: Parser a a peek :: Parser a a satisfy :: (a -> Bool) -> Parser a a check :: (a -> Bool) -> Parser a a +until :: (Parser a b) (Parser a c) -> Parser a [b] item :: a -> Parser a a | Eq a list :: [a] -> Parser a [a] | Eq a eof :: Parser a Void diff --git a/src/yard.icl b/src/yard.icl index 582ea1d..9ed6077 100644 --- a/src/yard.icl +++ b/src/yard.icl @@ -37,15 +37,15 @@ instance Applicative (Parser a) where instance Monad (Parser a) where bind p f = Parser \i -> case runParser p i of (Right r, rest) = runParser (f r) rest - (Left e, rest) = (Left e, rest) + (Left e, _) = (Left e, i) 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 e1, rest) = case runParser p2 i of - (Left e2, rest) = (Left $ e1+e2, rest) - (Right r, rest) = (Right r, rest) + (Left e2, rest) = (Left $ e1+e2, i) + (Right r, rest) = (Right r, rest) //Try the parser, if it fails decorate the error with Expected of the given String and position () :: (Parser a b) (String, Int) -> Parser a b @@ -66,6 +66,24 @@ peek = Parser \i -> case i of [] = (Left ParseError, []) [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 :: (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, [])