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  "path": "/t/haskells-missing-mutable-reference-type/14248#post_8",
  "publishedAt": "2026-06-09T16:51:34.000Z",
  "site": "https://discourse.haskell.org",
  "textContent": "Okay, I had to spend 40 minutes figuring out what this is, and I’m still not sure.\n\nAm I correct to understand that the problem you’re looking to solve is that of a user-definable implicit global context, which can be adjusted locally, e.g.\n\n\n    overriding :: Contextual a -> (a -> a) -> (forall b. IO b -> IO b) -- deeply magical\n\n    contextual x :: Contextual Int -- still magical\n    contextual x = 5\n\n    foo = do\n      a <- getContextual x\n      print a\n\n    --- Library user doesn't get to implement anything above this line\n\n    -- Prints number 7\n    main = overriding x (+2) foo\n\n\nI assumed if a feature like this were to exist it’d be on the compiler to collect all the “contextual” references upfront. This wouldn’t be mutable from user perspective, so I wouldn’t bring up `IORef` at all when talking about it.",
  "title": "Haskell's missing mutable reference type"
}