From: daniel@...42.com
Date: 2019-11-04T15:22:01+00:00
Subject: [ruby-core:95668] [Ruby master Feature#11660] a falsy value (similar to js undefined) that facilitates forwarding of default arguments

Issue #11660 has been updated by Dan0042 (Daniel DeLorme).


alanwu (Alan Wu) wrote:
> Since the beginning of time (correct me if I'm wrong), the two falsy values in Ruby has been `false` and `nil`, period.
> Adding another falsy value is a big change.

I Agree. Not saying there's no benefit, but this is too big a change for too small a benefit. Usually `nil` will play the role of the undefined value, so it might be nice if a method definition allowed something like `def foo(v ||= 42)`. But nowadays we have keyword arguments which do exactly what is needed in this case.

```ruby
def f2(x: 2)
  x
end

def f1(y:1, **kw)
  y + f2(**kw)
end

f1(y: 3) #=> 5
```

----------------------------------------
Feature #11660: a falsy value (similar to js undefined) that facilitates forwarding of default arguments
https://bugs.ruby-lang.org/issues/11660#change-82454

* Author: bughit (bug hit)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
I'll call it "missing" here.  Consider the following scenario:

```ruby
def foo(default1 = some_expression)
end

def bar(default1 = some_expression)
  foo default1
end

def foobar(default1 = some_expression)
  bar default1
end 
```

if you had "missing":

```ruby
def foo(default1 = some_expression)
end

def bar(default1 = missing)
  foo default1
end

def foobar(default1 = missing)
  bar default1
end 
```
missing passed as arg would be ignored (as if it wasn't passed at all)
and you wouldn't have to repeat the default value expression in every method

I believe that's how undefined works in js6 with respect to default args 




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