Yeah, it's a bit confusing; I think some tutorials/books do go over the `do` simplification steps. I guess conceptually `do` doesn't mean `Definitely a Monad`, it means `Maybe a Monad` or more `Probably should be a Monad, and if not, just remove the do!`. On Wed, 21 Feb 2024 at 09:18, Johannes Waldmann < johannes.waldmann@htwk-leipzig.de> wrote:
Dear Cafe,
I was surprised to see ghc accept this code
ghci> do let {x = False}; not x True
because I initially thought: there's a `do`, so there must be some monad, but which is it? some implicit Identity monad perhaps?
But the type is indeed plain `Bool`, and the explanation is (I think): there is a `do` but there is no monad, since the translation according to ( https://www.haskell.org/onlinereport/haskell2010/haskellch3.html#x8-470003.1... ) does never produce `(>>=)`.
So, all is fine, nothing to see here. Perhaps keep in mind as an edge case, useful to confuse students. Actually, to motivate them to read the language standard ...
- J.W. _______________________________________________ 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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