Partial Isomorphism - Hacker Log

Really curious about the best way to do isomorphism check, but with allowance for Maybe:

encodeRoute :: r -> FilePath
decodeRoute :: FilePath -> Maybe r

decodeRoute . encodeRoute = id in principle, but that Maybe is preventing us from treating this as isomorphism. What can be done here?

What's this https://github.com/hanshoglund/iso-deriving/blob/master/test/Spec.hs

https://github.com/schernichkin/partial-isomorphisms/blob/master/src/Control/Isomorphism/Partial/Unsafe.hs

data Iso α β
= Iso (α → Maybe β) (β → Maybe α)

https://www.mathematik.uni-marburg.de/~rendel/rendel10invertible.pdf

Hackish,

-- | An Iso that is not necessarily surjective; as well as takes an (unchanging)
-- context value.
type PartialIso ctx s a = (ctx -> a -> s, ctx -> s -> Maybe a)

partialIsoIsLawful :: PartialIso ctx s a -> ctx -> [a] -> Bool
partialIsoIsLawful (to, from) ctx =
  all $ \a -> let s = to ctx a in Just a == from ctx s

I think that paper will obviate needing a partialIsoIsLawful.

If I treat decoding routes as parsing, and encoding route as pretty-printing - that paper is super relevant to this problem.

More from Julien: https://github.com/srid/ema/issues/78#issuecomment-1036993190

Julien again, re: improving PartialIso: https://git.code.sourcephile.fr/~julm/webc/tree/main

ctx: https://github.com/srid/ema/issues/78#issuecomment-1041189041

isJust :: Maybe () <-> Bool
isJust = [biCase|
    Just () <-> True
    Nothing <-> False
  |]

whoa - this could be used defined bijecetive route encoders? https://hackage.haskell.org/package/invertible-0.2.0.7/docs/Control-Invertible-Monoidal.html