[ruby-core:91613] [Ruby trunk Feature#15618] Implement Enumerator::Yielder#to_proc

Issue #15618 has been reported by knu (Akinori MUSHA).

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Feature #15618: Implement Enumerator::Yielder#to_proc
https://bugs.ruby-lang.org/issues/15618

* Author: knu (Akinori MUSHA)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
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When writing an Enumerator block, you often want to delegate iteration to another method like this:

```ruby
enum = Enumerator.new { |y|
  Dir.glob("*.rb") { |file|
    File.open(file) { |f| f.each_line { |line| y << line } }
  }
}
```

I think this is such a common pattern, but the `{ |var| y << var }` part looks redundant compared to a normal iterator method being able to delegate to another method as simply as follows:

```
  def each(&block)
    @children.each(&block)
  end
```

So, I propose adding #to_proc to Yielder so you can directly pass a yielder object to another method as a block argument.

```ruby
enum = Enumerator.new { |y|
  Dir.glob("*.rb") { |file|
    File.open(file) { |f| f.each_line(&y) }
  }
}
```

Yielder is all about yielding, so I think it's pretty obvious what it means.

---Files--------------------------------
0001-Implement-Enumerator-Yielder-to_proc.patch (3.21 KB)


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