IORefCAS-0.2: Atomic compare and swap for IORefs and STRefs.

IORefCAS-0.2: Atomic compare and swap for IORefs and STRefs.

After GHC 7.2 a new `casMutVar#` primop became available, but was not yet exposed in Data.IORef. This package fills that gap until such a time as Data.IORef obsoletes it.

Further, in addition to exposing native Haskell CAS operations, this package contains "mockups" that imititate the same functionality using either atomicModifyIORef and unsafe pointer equality (in Data.CAS.Fake) or using foreign functions (Data.CAS.Foreign). These alternatives are useful for debugging.

Note that the foreign option does not operate on IORefs and so is directly interchangeable with CAS and Fake only if the interface in Class is used.

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