0.9.4 [2021.02.17]
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* Export `identity` from `Data.Interned.IntSet`.

0.9.3 [2020.09.30]
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* Add `Hashable` instances for `InternedString`, `InternedByteString`,
  `InternedText`, and `IntSet`.

0.9.2
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* Add a `Semigroup IntSet` instance.

0.9
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* Removed `identity` from the Interned class, to support applications where the identity is obtained by other means (e.g. a unique Ptr value)

0.8
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* Disabled cache removal as it was causing problems on large data sets. There is no good way to ensure that both references remain alive long enough to finish comparisons.
* Switched to IORef from MVar

0.7
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* Fixed problem where comparisons could happen between data structures while one was still a thunk, leading to equal structures comparing as inequal in limited circumstances, by appropriately using strictness annotations.

0.6
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* Widened the caches so they don't go through a single MVar per type. This has made a dramatic impact on performance. However, this broke the previous invariant that newer entries always had higher Ids than older entries.

0.5.2
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* Added Data.Interned.IntSet