Henning Thielemann <[EMAIL PROTECTED]> wrote: > > On Wed, 18 Jun 2008, Achim Schneider wrote: > > > Is there a generalisation of scan1, such that eg. > > > > foo (+) [0,1] (1,2) = [0,1,1,2,3,5,8,13,...] > > > > ? > > What is the (1,2) for? > Specifying the relative indexes an element depends on. Ideally, it should be generalised for n-ary functions.
> I could think of > foo f = List.unfoldr (\ xt@(x:xs) -> Just (x, xs ++ [f xt])) > > foo sum [0,1] = [0,1,1,2,3,5,8,13,21,34,... > I should elaborate: foo (+) [0,1,4] (1,2) = _|_, as 4 isn't 0+1 foo (+) [0,1] (2,3) = [0,1,_|_,1,_|_,_|_] foo (+) [0,1,1,2,3,5] (1,2) = [0,1,1,2,3,5,8,13,...] foo (+) [1] (1,1) = [1,2,4,8,16,32,...] If you allow for inverse functions, you could even say foo (+-) [0,...,3,..] (1,2) = [0,0,0,...,0,0,1,1,2,3,5,...] It seems like I'm searching for some primitive that lets me combine lists and currying. Think of passing a matrix, with each column (or row, if you prefer) separately uniquely typed, into a function. -- (c) this sig last receiving data processing entity. Inspect headers for past copyright information. All rights reserved. Unauthorised copying, hiring, renting, public performance and/or broadcasting of this signature prohibited. _______________________________________________ Haskell-Cafe mailing list [email protected] http://www.haskell.org/mailman/listinfo/haskell-cafe
