On Wed, Jun 27, 2007 at 02:26:05AM +0100, Ian Lynagh wrote:
dropPrefix :: Eq a => [a] -> [a] -> Maybe [a] dropPrefix [] ys = Just ys dropPrefix (x:xs) (y:ys) | x == y = dropPrefix xs ys dropPrefix _ _ = Nothing
Summary so far: Something should go in. The Maybe version seems more popular than generalisations, especially because Data.List already uses Maybe for the same sort of task in other functions. I don't think I tend to want the extra generality of Conor's leftFactor, and no-one else has "me-too"ed it either. Also, writing "(_, ([], zs))" rather than "Just zs" would be a bit cumbersome, so I think I'd like dropPrefix even if we also had leftFactor. Thus, based on the feedback thus far, I think dropPrefix as defined above should go in, with 'generalising Data.List functions' and 'implementing "leftFactor"' being left to possible future proposals. On names, Stefan wrote "I'd name it differently---not sure how", as the existing drop* functions always returns a list. Other names I considered were stripPrefix and removePrefix, but I can't think of any commonality between those names and existing functions off the top of my head. Thanks Ian