Zulip Chat Archive

Stream: general

Topic: Is this monad equation true?


François G. Dorais (Dec 04 2024 at 00:12):

Is this true?

[Monad m] [LawfulMonad m] (f : m α  m β) (x : m α) : x >>= f  pure = f x

I would love a proof if it is true.

François G. Dorais (Dec 04 2024 at 00:19):

Never mind. I found a counterexample right after pressing enter...

Mario Carneiro (Dec 04 2024 at 13:39):

this depends on some property of f, it's related to monotonicity in the domain theory sense

Mario Carneiro (Dec 04 2024 at 13:42):

or maybe lower semicontinuity, since it's saying that f x is the supremum of f (pure a) over all a <= x


Last updated: May 02 2025 at 03:31 UTC