On 02/10/2016 11:23 PM, David Menendez wrote:
For context, there’s currently a big thread about the type of ($), which is going to be more complicated in GHC 8.0 due to levity/runtime rep polymorphism. As I understand it, the intention is that this more complex type will be hidden unless a levity polymorphism flag is active. From my perspective, makes the question of whether this type is too complicated for beginners moot.
What puzzles me is that I still don’t understand what this feature is *for*.
[...]
So, is that it? Are there less-trivial levity-polymorphic functions? Is this a step on a road to new features, like [2]? Is there an article or something that makes the case for this?
Exactly. At least from my perspective, the value comes from unlifted data types. Given how much doubt levity polymorphism has received recently, I might write an article about it, but for now I recommend watching Richard's ICFP talk https://www.youtube.com/watch?v=bDdkeKr9vVw (Also, for those who understand Russian, we discussed levity polymorphism in the episode 10 of the Bananas and Lenses podcast http://bananasandlenses.net/episode010.) Roman