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Functional pearl: getting a quick fix on comonads
2015
SIGPLAN notices
A piece of functional programming folklore due to Piponi provides Löb's theorem from modal provability logic with a computational interpretation as an unusual fixed point. Interpreting modal necessity as an arbitrary Functor (in Haskell), the "type" of Löb's theorem is inhabited by a fixed point function allowing each part of a structure to refer to the whole. However, Functor's logical interpretation may be used to prove Löb's theorem only by relying on its implicit functorial strength, an
doi:10.1145/2887747.2804310
fatcat:iuxkqhvxnvdgnp4q4j5dmeznd4