问题
If I have a value a: Free[Op, A], is it possible to "flatten" the structure of a so that two Ops that are bound together by the free monad may be collapsed into one?
Context: I'd like to perform this as an optimization step before interpretation because a semantic of Op is that its operations are idempotent. So if two appear "in a row", the second can be eliminated at no cost to the semantics of the program.
回答1:
As far as I understand there is no way for this kind introspection of Free Monad program as it represents sequential computation where each step depends on the result of another.
There is a great talk by John de Goes about the pros and cons of Free Monad vs Free Applicative (https://www.youtube.com/watch?v=H28QqxO7Ihc). The latter gives power of introspection.
来源：https://stackoverflow.com/questions/39794492/optimizing-a-free-monad