Dear all, I came up with an idea to greatly simplify some kinds of array computations. It should work well with many kinds of arrays. Is this new? https://gist.github.com/4162375 These few days, I've been trying to rewrite a hydrodynamic simulation code that used Data.Vector (~250 lines), to Repa [1] . It seemed promising, but soon I realized that I needed to use Repa.map and Repa.zipWith almost everywhere. I need careful thinking to transform every lines (that used vector's indexing) to Repa's point-free stile. Is there any better ways? Then I realized that I was the author of Paraiso [2], a DSL for stencil computation. One of its feature is to write down array computation just as if it were scalar computation. Basically what I need is ZipList-like Applicative instances for vectors and Repa arrays. Why not they support ZipVector? Because 'pure' of zipList was an infinite list and you can't do infinite vectors. Then I came up with this idea. https://gist.github.com/4162375 the wrapper W does several things: it represents the 'pure,' homogeneous array in a space-efficient manner, and also serves as a newtype-wrapper of Num (and possibly Fractional, Floating...) instances. Questions are: is this technology new? or promising? doomed? It seems to me like a free-Applicative, like the free-Monad theory. Are they related? The function 'backend' helps to mix in the non-zip-like computations. How can we remove the 'undefined' in the 'backend?' Some of Repa computations are Monads. W needs to be a monad transformer to incooperate this. Also I'm grateful to past cafe discussion on existing Zippable implementations [3][4] . [1] hackage.haskell.org/package/repa [2] http://hackage.haskell.org/package/Paraiso [3] http://www.haskell.org/pipermail/haskell-cafe/2009-July/064403.html [4] http://hackage.haskell.org/packages/archive/category-extras/latest/doc/html/... -- Takayuki MURANUSHI The Hakubi Center for Advanced Research, Kyoto University http://www.hakubi.kyoto-u.ac.jp/02_mem/h22/muranushi.html