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Nov 5, 2013 at 17:57 history edited Noam Zeilberger CC BY-SA 3.0
added some explanation
Nov 5, 2013 at 4:35 comment added Noam Zeilberger @NoahS 𝔹 is the category of state types and state transformers. Traditionally in Hoare logic there is only state type, hence 𝔹 is a one-object category, i.e., a monoid (this restriction is not really necessary though). 𝔼 is the category of "predicates over states and proofs of Hoare triples". For example, if we identify predicates with subsets, then an arrow of 𝔼 from $P \subseteq S$ to $Q \subseteq S$ corresponds to a state transformer $c : S \to S$ such that $c(P) \subseteq Q$. Finally, $p : \mathbb{E} \to \mathbb{B}$ is just the forgetful functor.
Nov 5, 2013 at 4:03 comment added Noah Schweber What are $\mathbb{E}$ and $\mathbb{B}$?
Nov 4, 2013 at 22:21 comment added Andrej Bauer Your answer gives me the idea that we could view state transformers as paths in a space/type whose points/elements are states. Unfortunately, it cannot be that direct as paths are invertible but state transformers need not be. We need directed type theory.
Nov 4, 2013 at 22:15 history edited Noam Zeilberger CC BY-SA 3.0
notation/wording
Nov 4, 2013 at 22:09 history answered Noam Zeilberger CC BY-SA 3.0