On Sat, Mar 8, 2008 at 9:56 AM, Johan Tibell
My current implementation of the parser type is
newtype Parser r a = Parser { unParser :: S -> (a -> S -> Result r) -> (S -> Result r) -> Result r }
where the first parameter is the parse state, the second a success continuation, and the third a failure continuation. The only tricky part (except for the above mentioned problem) is to implement the choice operator. I implement mine as
instance Applicative (Parser r) where pure a = ... p <*> p' = Parser $ \s succ fail -> flip (unParser p s) fail $ \f s' -> unParser p' s' (succ . f) fail
Copied the wrong code, here's the implementation of <|> instance Alternative (Parser r) where empty = ... p <|> p' = Parser $ \s@(S _ pos) succ fail -> unParser p s succ $ \s'@(S _ pos') -> if pos == pos' then unParser p' s' succ fail else fail s' -- Johan