On Thu, Mar 15, 2012 at 06:18:39AM -0700, Simon Marlow wrote:
>
> Remove layers of newtype in Unique and Label
>
> Improves performance due to eliminating some unnecessary maps in
> e.g. mapToList, setToList. This was quite a significant effect in
> GHC.
It seems a pity we have to do that for performance reasons.
Would it be possible to instead have a way to write rules something like
map someCoercion = mkListCoercion someCoercion
(where mkListCoercion takes a coercion for x~y and gives you a coercion
for [x]~[y])?
Thanks
Ian
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