Issue #13820 has been updated by shevegen (Robert A. Heiler).


I am not sure that using a special-purpose operator would make a lot of sense.

I myself use nil primarily as means to indicate a default, "non-set" value. The
moment it is set to a boolean, be it false or true, is for me an indication
that it has been "upgraded" (or set by a user on the commandline etc...)

I do also tend to explicitely query for .nil? on some objects.

By the way, did you actually propose an actual syntax? The two '?'?

I do not think that ?? has any realistic chance for implementation due to
? already being used in ruby - in method definitions or ternary
operator for example. People may wonder why there are so many ? coming out
of nowhere. (For the record, I also consider || to be not pretty ... I 
strangely end up using a more verbose but explicit way to set or ensure
defaults in ruby code. I would never write a line such as "
port  = opts[:port] || (https ? 443 : 80)" simply because it takes my
brain too long to process what is going on there; my code always ends
up being so simple that I do not have to think about it much at all).

----------------------------------------
Feature #13820: Add a nill coalescing operator
https://bugs.ruby-lang.org/issues/13820#change-66203

* 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.



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