On Thu, Jul 14, 2011 at 11:29 AM, Christian Höner zu Siederdissen
<[email protected]> wrote:
> Hi,
>
> newtype Strand = Strand Int
>
> uses a single-constructor datatype "Int" as strand repr.
>
> While "Bool" is algebraic with two constructors. This is not optimized
> completely. Or maybe "was", I don't know the current status of GHC
> regarding this but I think it is still open.
Hmmm, using Int may or may not be better. Or maybe Word8, since we
only need one bit.
> So "True" is a pointer toward a global "True" with an indirection, while
> "true = Strand 0" would be an actual "0 :: Int#".
If your data type has something like
data X = X {..., strand :: !Strand, ...}
then, although not unpacked, the strand will always be a pointer
without indirections (i.e. not a thunk), right?
> And at least 1 year ago, I had much better performance using newtypes of
> Ints instead of "data Nuc = A | C | G | U"
I've seen this as well, but with an enumeration of more than 20
constructors. But it's not like Strand is the bottleneck of some
application, I think. My concern is about losing readability without
gaining anything measurable in real tests. ADTs are really nice =).
Cheers, =D
--
Felipe.
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