From: shannonskipper@...
Date: 2019-11-12T19:44:51+00:00
Subject: [ruby-core:95822] [Ruby master Feature#16341] Proposal: Set#to_proc	and Hash#to_proc

Issue #16341 has been updated by shan (Shannon Skipper).


Nondv (Dmitry Non) wrote:
> Speaking of hashes, they could implement implicit proc conversion as well:
> 
> ```ruby
> class Hash
>   def to_proc
>     ->(key) { self[key] }
>   end
> end
> 
> dogs = ['Lucky', 'Tramp', 'Lady']
> favourite_food = { 'Lucky' => 'salmon', 'Tramp' => 'pasta', 'Lady' => 'pasta' }
> 
> food_to_order = dogs.map(&favourite_food)
> ```

This already works! Hash#to_proc was added in Ruby 2.3. [ruby-core:11653](https://bugs.ruby-lang.org/issues/11653)

I like the idea of Set#to_proc.

----------------------------------------
Feature #16341: Proposal: Set#to_proc and Hash#to_proc
https://bugs.ruby-lang.org/issues/16341#change-82651

* 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]
```

**UPD**

also for hash:

```ruby
class Hash
  def to_proc
    ->(key) { self[key] }
  end
end

dogs = ['Lucky', 'Tramp', 'Lady']
favourite_food = { 'Lucky' => 'salmon', 'Tramp' => 'pasta', 'Lady' => 'pasta' }

food_to_order = dogs.map(&favourite_food)
```



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