Using Monad Transformers without understanding them
summary
Explains how to drop manual boxing and use ExceptT, ReaderT, and StateT to add errors, read-only config, and mutable state to existing monads, with runnable PureScript examples in a repo. Shows concrete bind/run functions, provides ask/get/put/throwError/catchError helpers, and demonstrates stack-order difference: ExceptT stacked over StateT drops state on error while StateT over ExceptT preserves it. Covers Tagless Final as an encoding and includes code to run each transformer variant.
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chapters (11)
- 0:00Introduction to monads
- 1:06What problems do monads solve
- 5:01Limitations of basic monads
- 6:17Understanding transformers
- 8:46The problem of manual nesting
- 12:40ExceptT transformer
- 14:54ReaderT transformer
- 16:52StateT transformer
- 19:02Using transformers effectively
- 20:46Stack order and monads
- 23:11Conclusion and resources
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