[Haskell-cafe] what monad is this?

[Noon van der Silk]

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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