From: non.dmitriy@...
Date: 2019-11-11T15:18:26+00:00
Subject: [ruby-core:95791] [Ruby master Feature#16341] Proposal: Set#to_proc

Issue #16341 has been updated by Nondv (Dmitry Non).


Well, `to_proc` allows to send objects as blocks which can be quite useful not just in case of `select`/`reject`. Also, probably, those two are used more often than `grep`/`grep_v`.

Another example from the top of my head is `count`:

```ruby
dogs = Set[:labrador, :husky, :bullterrier, :corgi]
pets = [:parrot, :labrador, :goldfish, :husky, :labrador, :turtle]
pets.count(&:dogs) # ===> 3
```

----------------------------------------
Feature #16341: Proposal: Set#to_proc
https://bugs.ruby-lang.org/issues/16341#change-82612

* Author: Nondv (Dmitry Non)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
``` ruby
class Set
  def to_proc
    -> (x) { include?(x) } # or method(:include?).to_proc
  end
end
```

Usage:

```ruby
require 'set'

banned_numbers = Set[0, 5, 7, 9]
(1..10).reject(&banned_numbers) # ===> [1, 2, 3, 4, 6, 8, 10]
```



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