Monad transformer library with type indexes, providing 'free' copies.

Latest on Hackage:0.1.6

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BSD3 licensed by Mark Snyder
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A monad transformer library with type indexes, which allows the programmer to get a distinct copy of one of the monads without reproducing definitions and instances. It currently supports IdentityX, ReaderX, StateX, WriterX, RWSX, and ErrorX monads (and their transformer versions). All these copies can be combined into a transformer stack, including any of the original mtl monads. Inspired by the original mtl. That library was inspired by the paper /Functional Programming with Overloading and Higher-Order Polymorphism/, by Mark P Jones (, Advanced School of Functional Programming, 1995. See the Examples.hs file for usage.

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