On Wed, Nov 11, 2009 at 5:28 PM, Tillmann Vogt <tillmann.v...@rwth-aachen.de > wrote:
> Hi, > > I tried to use unboxed arrays for generating an antialiased texture. To > make it easier to understand, here is the stripped down code that produces > an error: > > >import Control.Monad.ST > >import Data.Array.ST > >import Data.Array.Unboxed > >import Data.Word > >type BitMask = UArray Int Word16 -- for determining the grey value of a > pixel > >type Pixels = (Int, Int, T) > >data T = N | B BitMask -- this does not work > >-- type T = Int -- this works if int the next line N is replaced by ..lets > say 0 > >f = newArray (0,10) N :: (ST s (STUArray s Int T)) > > > http://hackage.haskell.org/packages/archive/array/0.2.0.0/doc/html/Data-Array-MArray.html#t%3AMArray > shows that mutable/unboxed arrays only allow simple types: > i.e. MArray (STUArray s) Int32 (ST s) > > Isn't this ugly? Imagine this would be the case in C: > > > struct stupidArrayElement{ > int a; > int b; // not allowed! > } > > stupidArrayElement s[10]; > > > Wouldn't it be nice to have something like: MArray (STUArray s) e (ST s) > with e being a non-recursive data type (like data T = N | B Bitmask). > My understanding of Haskell isn't deep enough to know if I have overlooked > something or if the problem is solvable without a language extension. With a > language extension I guess that it is not hard to find out if an abstract > data type is non-recursive. Then this type should be serializable > automatically. > > What do you think? > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > Actually, there's a cool package called storable record. Could it be of some use to you? (Perhaps you *might* be able to use it if the BitMasks are of uniform length). Am not 100% sure though. Isn't this ugly? I am not sure if it is really *ugly*... and if am allowed to nit-pick, the analogy with C is not appropriate either. Arrays are just different. (At least thats how I console myself, when am looking for a high performance strict array). Also, on an approximately related issue, I was suggested to look into data parallel arrays.
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