<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="">We now have a revised version of the ”Or pattern” proposal #43 to consider:<div class=""><br class=""></div><div class=""> (formatted) <a href="https://github.com/osa1/ghc-proposals/blob/or_patterns/proposals/0000-or-" class="">https://github.com/osa1/ghc-proposals/blob/or_patterns/proposals/0000-or-</a>patterns.rst<br class=""> (PR thread) https://github.com/ghc-proposals/ghc-proposals/pull/43</div><div class=""><br class=""></div><div class="">You may remember that we discuss this a while back</div><div class=""><br class=""></div><div class=""> <a href="https://mail.haskell.org/pipermail/ghc-steering-committee/2017-November/000231.html" class="">https://mail.haskell.org/pipermail/ghc-steering-committee/2017-November/000231.html</a></div><div class=""><br class=""></div><div class="">and finally decided to bounce it back to the authors with the following recommendation:</div><div class=""><br class=""></div><div class=""> <a href="https://github.com/ghc-proposals/ghc-proposals/pull/43#issuecomment-358189327" class="">https://github.com/ghc-proposals/ghc-proposals/pull/43#issuecomment-358189327</a></div><div class=""><br class=""></div><div class="">We previously decided that we are inclined to accept this proposal if the authors change the points that we highlighted. Judging from the conversation of SimonPJ and Richard with the author on the GitHub thread, it appears to me that most of the issues have been addressed. However, Simon’s point </div><div class=""><br class=""></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div class=""><div class=""><span class="Apple-tab-span" style="white-space:pre"> </span>• "Patterns that bind existentials, dictionaries, or equalities are rejected by the type checker". I disagree. Earlier I suggested "no variable bound by an or-pattern can have a type that mentions an existential variable bound by the or-pattern". That is much more friendly because you can still match against an existential constructor; you just can’t bind an existential variable.</div></div><div class=""><br class=""></div></blockquote>from <<a href="https://github.com/ghc-proposals/ghc-proposals/pull/43#issuecomment-368933401" class="">https://github.com/ghc-proposals/ghc-proposals/pull/43#issuecomment-368933401</a>> still doesn’t seem to be addressed, or am I misunderstanding?<div class=""><br class=""></div><div class="">Overall, I propose to accept the proposal, possibly requiring that the above point be addressed.<br class=""><div class=""><br class=""></div><div class="">What do you all think?</div><div class=""><br class=""></div><div class="">Cheers,</div><div class="">Manuel</div><div class=""><br class=""></div></div></body></html>