Notably, it is not always useful to suggest removing the `do`, e.g. I will often write that exact same `do` block with a let in it in tests, because it is very often the case that later down the line I do end up wanting to use binds/stop using binds in the `do` block, and I personally think the syntactic noise in the git diffs is not worth the (purely aesthetic?) benefit of not having the `do`. It's also useful if you're a fan of "abusing"(?) BlockArguments+`do` to turn f   (foo bar baz)   (u v) to f   do foo bar baz   do u v On 2/21/24 17:27, Mark McConnell via Haskell-Cafe wrote:

To my surprise, hlint (version 3.3.6) did not suggest taking out the do.  I ran the following through hlint.

jk :: Bool jk = do   let x = False   not x

On Wednesday, February 21, 2024 at 04:23:49 AM EST, Noon van der Silk wrote:

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 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.

-- Noon van der Silk

http://silky.github.io/

"My programming language is kindness." _______________________________________________ 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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