[Haskell-cafe] what monad is this?

[Georgi Lyubenov]

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 
> <noonsilk at gmail.com> 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 
> <johannes.waldmann at 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#x8-470003.14
>     )
>     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.
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>
>
> -- 
> Noon van der Silk
>
> http://silky.github.io/
>
> "My programming language is kindness."
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