minh thu
But for some functions, it can be seen clearly that such information could have been constructed at the same time that the data structure.
So it is related to fusion techniques, but with the additional possibility of adding fields to the original data structure.
Well, the point fusion is about is _not_ to construct lists. consider naiveDropEnd xs = take (length xs - 1) xs , which, due to length being a catamorphism, traverses xs twice. It can be, in fact, reduced to the more sensible dropEnd (x:[]) = [] dropEnd (x:xs) = x:dropEnd xs , but that requires getting rid of the fold by replacing Integers with Peanos: length' = map (\_ -> ()) pred = tail succ = (():) zarroo = [] Now we can write notSoNaiveDropEnd xs = take' (pred $ length' xs) xs , which can be fused into a single y-combinator. Morale of the story: Folds are the bane of laziness. Having some magic in place than can choose a lazily constructed (and fused) Peano instance for Num in the right places would be awesomely cool. -- (c) this sig last receiving data processing entity. Inspect headers for copyright history. All rights reserved. Copying, hiring, renting, performance and/or quoting of this signature prohibited.