HOW I UNDERSTOOD MONAD TRANSFORMERS

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" summary

Mixing Future[Option[A]] in for-comprehensions becomes concrete: code shows a custom wrapper that maps and flatMaps the inner Option rather than the outer Future, then generalizes to a parametric OptionT using Functor/FlatMap/Applicative typeclass instances (cats) and implicits. The live coding reveals the need for an ExecutionContext for Future instances, how to lift/pure values, and tradeoffs: extra allocations hurt tight loops and don’t belong in public APIs if hiding cats types.

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" chapters (13)

1. 0:00Introduction
2. 1:03Example
3. 5:58Implicit Switch
4. 8:27Effect Type
5. 10:06Internal Wrapper
6. 14:28Future Wrapper
7. 27:50Implicit
8. 28:42Functor
9. 30:32Flat Map
10. 32:45Applicative
11. 35:28Dependency
12. 37:28OptionT
13. 39:18Compiler Error

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