0.6.1
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* Added `tryReadMVar` for read-only `MVar`s.

0.6
---

* Write-only types are no longer `Eq`, but are now contravariant functors.

0.5
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* Read-only types are no longer `Eq`, but are now functors.

0.4
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* Functions are low lifted to `MonadBase IO`.

0.3
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* Initial version with read-only and write-only versions of `Chan`, `MVar`,
  `TChan`, `TMVar` and `TVar`.