<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Sorry to say that I do not like this proposal in its current form, as I elaborate on GitHub: <br class=""><div><a href="https://github.com/ghc-proposals/ghc-proposals/pull/216#issuecomment-598191928" class="">https://github.com/ghc-proposals/ghc-proposals/pull/216#issuecomment-598191928</a></div><div><br class=""></div><div>Richard</div><div><br class=""><blockquote type="cite" class=""><div class="">On Mar 12, 2020, at 8:16 AM, Vitaly Bragilevsky <<a href="mailto:bravit111@gmail.com" class="">bravit111@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">I support this proposal in the current form. I am especially happy<br class="">with the idea that the 'M.do' qualifier does not affect the 'return'<br class="">function. It's just fine to affect implicit constructions exclusively.<br class=""><br class="">Vitaly<br class=""><br class="">ср, 11 мар. 2020 г. в 21:37, Joachim Breitner <<a href="mailto:mail@joachim-breitner.de" class="">mail@joachim-breitner.de</a>>:<br class=""><blockquote type="cite" class=""><br class="">Dear Committe,<br class=""><br class="">Proposal:<br class=""><a href="https://github.com/tweag/ghc-proposals/blob/local-do/proposals/0000-local-do.rst" class="">https://github.com/tweag/ghc-proposals/blob/local-do/proposals/0000-local-do.rst</a><br class=""><br class="">Discussion: https://github.com/ghc-proposals/ghc-proposals/pull/216<br class=""><br class=""><br class="">Summary:<br class=""><br class="">last June we looked at a “local do” proposal that would be a more<br class="">targetted variant of RebindableSyntax, just for “do”. After an initial<br class="">acceptance recommendation from me we had some good discussion, and<br class="">eventually sent it back for revision. One problem, among many, was that<br class="">the story around type inference wasn’t as good as with normal “do”.<br class=""><br class="">All attempts to give meaning to “do” via a local value (e.g. a record,<br class="">or type classes etc.) were unsatisfying in one way or another. (Often<br class="">something about mumble impredicative types mumble.)<br class=""><br class="">Anyways, Facundo Domínguez joined the author team and the discussion<br class="">steered towards a less ambitious, but simpler and cleaner proposal:<br class="">Qualified do. The idea is simply to treat a module qualifier on the do<br class="">keyword as a qualified on all the implicit :<br class=""><br class=""> M.do { x <- u; stmts } = (M.>>=) u (\x -> M.do { stmts })<br class=""><br class="">and similar for the other monad desugaring rules.<br class=""><br class=""><br class="">Recommendation:<br class=""><br class="">This seems simple, convenient and easy to understand, so I recommend<br class="">accepting the proposal.<br class=""><br class=""><br class="">Comment:<br class=""><br class="">There was some discussion if<br class=""><br class=""> M.do { return x } = M.return x<br class=""><br class="">but it seems that changing the meaning of more than `do` it self may be<br class="">more confusing than helpful, so the proposal as it stands does _not_<br class="">propose it (see Alternatives). I wish we had a better story here, and<br class="">welcome ideas from the committee.<br class=""><br class=""><br class="">WDYAT?<br class=""><br class=""><br class="">Cheers,<br class="">Joachim<br class=""><br class=""><br class="">--<br class="">Joachim Breitner<br class=""> mail@joachim-breitner.de<br class=""> http://www.joachim-breitner.de/<br class=""><br class=""><br class="">_______________________________________________<br class="">ghc-steering-committee mailing list<br class="">ghc-steering-committee@haskell.org<br class="">https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee<br class=""></blockquote>_______________________________________________<br class="">ghc-steering-committee mailing list<br class=""><a href="mailto:ghc-steering-committee@haskell.org" class="">ghc-steering-committee@haskell.org</a><br class="">https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee<br class=""></div></div></blockquote></div><br class=""></body></html>