As the title says, is it possible to prove a view function returned a certain result in a past block?
For example let's have a view function
a(). Let this be block 90, can I know if
a() returned a certain result (e.g. true/false) at block 80? I'd like to get a cryptographic proof of it.
For clarity, are you trying to access this historical value within a smart contract transaction or are you trying to prove it in an off-chain application?
I'd need to get an on-chain verifiable proof in SOME way. The historical value itself can and will be accessed off-chain. I.e. I can have off-chain clients get the result at the given block.