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The composition operator ◦ there is only conceptually correct up to Applicative instances. Monad Transformers rely on very specifically tailored composition, a
by Peaker 12y ago
The composition operator ◦ there is only conceptually correct up to Applicative instances. Monad Transformers rely on very specifically tailored composition, and not a generic Type-Compose. Otherwise we could just type-compose Writer, State, etc and wouldn't need WriterT, StateT, ...
- tel 12y agoTrue and important, though honestly I just think of it (very loosely) as a functor composition operator and note that the composition happens to be a monad as well.