From: shevegen@... Date: 2018-06-27T08:18:44+00:00 Subject: [ruby-core:87653] [Ruby trunk Feature#14709] Proper pattern matching Issue #14709 has been updated by shevegen (Robert A. Heiler). zverok wrote an add-on in regards to "syntax proposal" here: https://zverok.github.io/blog/2018-06-26-pattern-matching.html I don't have a suggestion for a better syntax myself really. zverok suggested, among other examples, e. g. this: case (lat, *lng) when (Numeric, Numeric => lng, Hash => opts) I am not a huge fan of the (). :P However had, I was also thinking ... pattern matching is in some ways similar to regex-checking, yes? For regexes we have =~. Perhaps we could use a similar construct for pattern matching, also starting with =. Not sure about the second character. =| might be almost an obvious choice since it looks like a pipe in a way, but I am not sure if this can be used. One could also ponder about a combination of three characters, a bit like the somewhat new one used for lambdas. ->| or ->~ ... not that any of these are very pretty. And one thing I also always mentioned is that it should not be too hard to visually differentiate between different things in ruby code so perhaps something like ->~ is a bad idea since it is not so easy to see any difference. But two characters may be fine, like the regex variant or also the compound ones like += or -= (two characters seem better than more than two characters). ---------------------------------------- Feature #14709: Proper pattern matching https://bugs.ruby-lang.org/issues/14709#change-72673 * Author: zverok (Victor Shepelev) * Status: Closed * Priority: Normal * Assignee: * Target version: ---------------------------------------- On RubyKaigi 2017, there was a [presentation](http://rubykaigi.org/2017/presentations/yotii23.html) of Yuki Torii about possible implementation of pattern matching. The syntax proposed in presentation was: ```ruby res = [:ng, 500] case res when %p([:ng, status]) p status end ``` The proposed syntax seem to feel pretty consistent, and the implementation (forked Ruby interpreter) was working at this moment. As @ko1 was one of the contributors to the experiment, I don't suppose Ruby core team is not aware of the proposal, so I'd like to know what the status of it? Are there some plans for full-strength pattern matching in Ruby 3 (with proposed, or any other, syntax)? PS: There are many existing gems with some kind "almost real" pattern matching (including recently emerged [Qo](https://github.com/baweaver/qo)), yet I believe that the _only_ useful pattern matching can be provided language core. Otherwise, two main goals can't be achieved: * reasonable performance (as the pattern-matching is useful mostly in complicated algorithms, which tend to repeat matches thousands of times); * unpacking of parts of the patterns into local variables. -- https://bugs.ruby-lang.org/ Unsubscribe: