Stephane Bortzmeyer wrote:
Parsec provides "count n p" to run the parser p exactly n times. I'm looking for a combinator "countBetween m n p" which will run the parser between m and n times. It does not exist in Parsec.
infixr 2 <:> (<:>) = ap . ap (return (:)) countBetween 0 0 _ = return [] countBetween 0 n p = p <:> countBetween 0 (n-1) p <|> return [] countBetween m n p = p <:> countBetween (m-1) (n-1) p (Shortest solution yet, I think. Is primitive recursion somehow out of fashion? Should I rewrite it as two folds?)
Does anyone has a solution? Preferrably one I can understand, which means not yet with liftM :-)
As requested, though I believe a quick 'liftM2' would have been easier than two 'ap's. But if you prefer: a <:> b = do x <- a y <- b return (a:b) or what I'd ordinarily use: (<:>) = liftM2 (:) Udo. -- As Will Rogers would have said, "There is no such thing as a free variable."