[ruby-core:91221] [Ruby trunk Feature#13807] A method to filter the receiver against some condition

Issue #13807 has been updated by sawa (Tsuyoshi Sawada).


I came up with an idea better than this (https://bugs.ruby-lang.org/issues/15557).

So I withdraw this proposal. Please close it.

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Feature #13807: A method to filter the receiver against some condition
https://bugs.ruby-lang.org/issues/13807#change-76459

* Author: sawa (Tsuyoshi Sawada)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
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I frequently see code that uses some value if that value satisfies a certain condition, and something else otherwise.

```ruby
a.some_condition ? a : b
```

And in most cases, the value of `a` is non-nil when the condition is satisfied.

I propose to have a method, perhaps named `verify`, which would implemented to be equivalent to this definition:

```ruby
class Object
  def verify
    self if yield(self)
  end
end
```

Then, we can write the expression above (assuming `a` is non-nil when the condition is satisfied) like this:

```ruby
a.verify{|a| a.some_condition} || b
```

Perhaps it would also be useful to do something like:

```ruby
a.verify{|a| a.some_condition}&.chaining_of_more_methods
```



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