On 2/5/20 1:18 PM, Emil Axelsson wrote:
Den 2020-02-05 kl. 17:40, skrev Tom Schouten:
I think there is probably a use for a generic library that can do this kind of sharing recovery. Still I'm not quite happy with the "can be unsafe in some cases" remarks and would like to learn more. However there might be a tradeoff to use this as a simplified interface to something that is implemented in a safe monadic style under the hood.
Here's the generic library that Kansas Lava uses for sharing recovery:
https://hackage.haskell.org/package/data-reify
The original Observable Sharing paper explains in more detail the properties of observable sharing:
https://www.researchgate.net/profile/David_Sands3/publication/225679607_Obse...
Basically, the worst thing that can happen is that you get less sharing (and maybe in some cases even more) than you expect because of whether or not GHC decides to inline something. Also, beware that overloaded definitions may not be shared due to the extra dictionary argument.
In practice, I've had very few surprises with observable sharing. But of course, the risk of unexpected duplication is not ideal when we're talking hardware :-)
/ Emil
Thanks That unpredictable nature doesn't sit well with me :)