[Haskell-cafe] Does GHC compare pointers when eval'ing (==)

Johan Tibell johan.tibell at gmail.com
Wed Aug 20 08:28:55 UTC 2014


On Wed, Aug 20, 2014 at 10:23 AM, Erik Hesselink <hesselink at gmail.com>
wrote:

> As I understood, the question was if GHC would first compare pointers,
> and only call the Eq instance if the pointers are not equal. I guess
> this would be safe, but I don't think GHC does such a thing.


I think the reason it isn't done is that it's not always an optimization.
We do it manually in e.g. bytestring.
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