Derive HasReader from HasState

tweag / capability

Extensional capabilities and deriving combinators

BSD 3-Clause "New" or "Revised" License

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Closed aherrmann closed 6 years ago

aherrmann commented 6 years ago

Moves ReaderIORef to a separate module to avoid circular imports
Defines ReadState/ReadStatePure combinators to derive HasReader from HasState.
- Note, local requires to modify the state. Care needs to be taken to ensure that local is correct in the context of exceptions. ReadState uses MonadMask to that end. ReadStatePure can be used in cases where MonadMask is not available and exceptions cannot be caught in the monad.

aherrmann commented 6 years ago

I'll address the module structure in another PR.