Christopher Done <chrisd...@gmail.com> writes: > Anyone ever needed this? Me and John Wiegley were discussing a decent > name for it, John suggested inv as in involution. E.g. > > inv reverse (take 10) > inv reverse (dropWhile isDigit) > trim = inv reverse (dropWhile isSpace) . dropWhile isSpace > > That seems to be the only use-case I've ever come across.
And it's here only because reverse^-1 ≡ reverse, is not it? I only can see how f ∘ g ∘ f^-1 can be a pattern. > There's also this one: > > co f g = f g . g > > which means you can write > > trim = co (inv reverse) (dropWhile isSpace) > > but that's optimizing an ever rarer use-case. -- lelf _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
