From: nobu@... Date: 2017-08-18T00:16:35+00:00 Subject: [ruby-core:82419] [Ruby trunk Feature#13820] Add a nill coalescing operator Issue #13820 has been updated by nobu (Nobuyoshi Nakada). williamn (William Newbery) wrote: > shevegen (Robert A. Heiler) wrote: > > By the way, did you actually propose an actual syntax? The two '?'? > > Not really personally set on any given syntax, just `??` and `//` are familiar to me from other programming. Although actually for `??` specifically, I guess the fact Ruby uses it in both methods and ternary causes a conflict rather than just one or the other (`x.nil?? "was nil" : "not nil"`). I wouldn't know if the parser can figure that out or not. `??` is a string literal, and `//` is a regexp literal. > ```ruby > def fetch(id, **opts) > host = opts[:host] || default_host > https = opts[:https] || true > port = opts[:port] || (https ? 443 : 80) Why not keyword arguments? ---------------------------------------- Feature #13820: Add a nill coalescing operator https://bugs.ruby-lang.org/issues/13820#change-66224 * Author: williamn (William Newbery) * Status: Open * Priority: Normal * Assignee: * Target version: ---------------------------------------- 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: