ghci> :set -XBlockArguments ghci> let be = id in do be do be do () () On Wed, Feb 21, 2024 at 3:18 AM 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.