unboxed arrays restricted to simple types (Int, Float, ..)
Tillmann.Vogt at rwth-aachen.de
Wed Nov 11 06:58:12 EST 2009
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:
>type BitMask = UArray Int Word16 -- for determining the grey value of
>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))
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:
int b; // not allowed!
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
What do you think?
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