Maybe it should somehow replace "osiudfhg" with "x1_of", but how is it supposed to know that? It is a library function, after all.

My understanding was that the user would ask for a refactoring by explaining the isomorphism between two data types. I just remembered that Facebook open-sourced something called Retrie that they use to refactor their own Haskell code. That should give a solid lower bound on what is possible. On Wed, May 24, 2023 at 8:02 AM MigMit wrote:

I don't think that's possible. Assume that there is a library that contains a module Stupid with a function osiudfhg, which is actually the same as fst:

module Stupid where osiudfhg :: (a, b) -> a osiudfhg (a, _) = a

If Alice uses that library, then her code could look like

main = putStrLn "print some magic number" >> print ( osiudfhg v )

How is Bob's code supposed to look? Maybe it should somehow replace "osiudfhg" with "x1_of", but how is it supposed to know that? It is a library function, after all.

Yes, it might analyze source code of the Stupid module, but this is a daunting task.

...

On 24 May 2023, at 14:52, profited--- via Haskell-Cafe < haskell-cafe@haskell.org> wrote:

let's consider this example Alice has 1.hs like this v :: (,) Int Bool v = (,) 0 False

main :: IO () main = putStrLn "print some magic number" >> print ( fst v )

Bob download 1.hs from Alice

Bob would like to change 1.hs to 2.hs Bob want the programs [ 1.hs 2.hs ] to behave the same

the reason that Bob want to modify 1.hs may be Bob does not like the type (,) in 1.hs

Bob has Vector_2.hs module Vector_2 where

data Vector_2 a b = C a b

x1_of :: Vector_2 a b -> a x1_of ( C x1 _ ) = x1

x2_of :: Vector_2 a b -> b x2_of ( C _ x2 ) = x2

Bob like his Vector_2.hs Bob thinks the Vector_2 shall be good enough to replace (,) in 1.hs

i want to create a translator.hs for Bob Bob tell the translator.hs that Bob want to replace (,) with Vector_2 in 1.hs translator.hs automatically translate 1.hs to 2.hs 2.hs shall look like this import Vector_2 ( Vector_2 ) import qualified Vector_2

v :: Vector_2 Int Bool v = Vector_2.C 0 False

main :: IO () main = putStrLn "print some magic number" >> print ( Vector_2.x1_of v )

what shall i do ? _______________________________________________ Haskell-Cafe mailing list To (un)subscribe, modify options or view archives go to: http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe Only members subscribed via the mailman list are allowed to post.

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