From: lamont@... Date: 2021-03-15T23:50:08+00:00 Subject: [ruby-core:102877] [Ruby master Feature#13820] Add a nil coalescing operator Issue #13820 has been updated by lamont (Lamont Granquist). This would cut down on a lot of bugs dealing with lazy initialization of values where `false` is valid and needs to be remembered: ``` # hammers on the expensive determination method if it returns false def should_dosomething? @should_dosomething ||= expensively_determine_if_should_do_something end # correctly remembers either false or true def should_dosomething? @should_dosomething ??= expensively_determine_if_should_do_something end ``` This happens more than you might expect because people learn to use `||=` in that situation and wind up accidentally writing the buggy code when they're faced with this problem of remembering an expensive thing that returns booleans. The ??= operator should be introduced into the language and really the idiom should switch to consistently use it all the time to avoid this bug. ---------------------------------------- Feature #13820: Add a nil coalescing operator https://bugs.ruby-lang.org/issues/13820#change-90938 * Author: williamn (William Newbery) * Status: Open * Priority: Normal ---------------------------------------- It would be nice if Ruby had an operator that only considered `nil` as false, like the null coalescing operators or "Logical Defined-Or operator" (Perl) found in some other languages. Ive seen things like `//` and `//=`m `??` and `??=`, or `?:` used for this. This would work like `||` and `||=` for short circuiting etc. except that only `nil` is considered a false condition. While Ruby considers only "false" and "nil" as false, with everything else true ("", [], {}, etc.) I still find occasionally people trip up when using logical or, `||` and `||=` when the value may be false. ```ruby a = 0 || 55 # = 0 Ruby already considers 0, "", etc. as true (oter languages do differ a lot here) a = 0 ?? 55 # = 0 So no change here a = nil || 55 # = 55, nil is false so right side is evaulated. a = nil ?? 55 # = 55, again no change a = false || 55 # = 55, however false is false for logical or a = false ?? 55 # = false, but its still a non-nil value ``` For example when doing things like: ```ruby def lazy @lazy ||= compute_this end def fetch(id, **opts) host = opts[:host] || default_host https = opts[:https] || true port = opts[:port] || (https ? 443 : 80) ... ``` Normally the intention is to use a default value or compute an action if no value is provided, which if the value may be false then requires special handling, or sometimes is missed and results in a bug. -- https://bugs.ruby-lang.org/ Unsubscribe: