UP YOUR MTL GAME WITH CLASSY OPTICS
summary
Claims that replacing monad transformers with MTL plus classy optics removes lifting, keeps polymorphic F, and derives instances (Reader/State/Error) via generated lenses/prisms. Implements applicative ask and MonadError derivation for nested config and a PaymentError ADT, maps business errors to HTTP responses in production since Sept 2018, and materializes programs with a RIO-style newtype or zero/Task. Works in practice but increases cognitive load; recommends using a small subset (ask, MonadError), Ref for state, and module-based interpreters.
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chapters (14)
- 0:00Intro
- 0:43What is MTL
- 5:48What is Classy Optics
- 15:25Remo
- 16:46Zero
- 17:22Example
- 19:05Benefits and drawbacks
- 19:56Personal recommendation
- 21:28Avoid this
- 21:52Create modules
- 22:12Time Apps
- 23:31Refactoring
- 24:19Disclaimer
- 24:57Legality
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