From: halostatue@...
Date: 2020-12-11T03:38:22+00:00
Subject: [ruby-core:101409] [Ruby master Feature#17333] Enumerable#many?

Issue #17333 has been updated by austin (Austin Ziegler).


Like Daniel in #note-10 and Sawa in #note-6, I don���t think that this is a great choice, although `many?` is surprisingly complex to implement efficiently. The simplest Ruby implementation I could come up with is this:

```ruby
  def many?
    reduce(false) { |f, v|
      vp = block_given? ? yield v : v
      break true if f && vp
      vp
    }
  end
```

It���s probably a little less efficient than the ActiveSupport extension (which uses two different branches for `block_given?` or not). Something similar was recently suggested to the Elixir core list, and what was decided there is I think a little more generalizable, `count_until` (https://github.com/elixir-lang/elixir/pull/10532).

Here���s a Ruby implementation of what could be Enumerable#count_until?

```ruby
  def count_until(limit, match = nil, &block)
    cnt = 0

    if match
      warn 'warning: given block not used' if block
      block = ->(v) { v == match }
    elsif !block
      return [limit, count].min if respond_to?(:size)
      block = ->(_) { true }
    end

    stop_at = limit - 1

    reduce(0) { |c, v|
      c += 1 if block.(v)

      break limit if c == stop_at

      c
    }
  end

  # (1..20).count_until(5) # => 5
  # (1..20).count_until(50) # => 20
  # (1..10).count_until(10) == 10 # => true # At least 10
  # (1..11).count_until(10) == 10 # => true # At least 10
  # (1..11).count_until(10 + 1) > 10 # => true # More than 10
  # (1..5).count_until(10) < 10 # => true # Less than 10
  # (1..10).count_until(10 + 1) == 10 # => true # Exactly ten
```

This could be easily implemented as `count(until: 10)` or `count(2, until: 10)` or `count(match: 2, until: 10)` instead of a different method entirely.

(Sorry if this ends up showing up twice; I sent it first by email, but it appears that my email never made it.)

----------------------------------------
Feature #17333: Enumerable#many?
https://bugs.ruby-lang.org/issues/17333#change-89171

* Author: okuramasafumi (Masafumi OKURA)
* Status: Open
* Priority: Normal
----------------------------------------
`Enumerable#many?` method is implemented in ActiveSupport.
https://api.rubyonrails.org/classes/Enumerable.html#method-i-many-3F
However, it's slightly different from Ruby's core methods such as `one?` or `all?`, where they take pattern argument.
I believe these methods should behave the same so that it's easier to guess and learn.

We already have `none?`, `one?`, `any?` and `all?`, which translate into `== 0`, `== 1`, `> 0` and `== self.size`.
`many?` method translates into `> 1`, which is reasonable to exist.
Currently we need to write something this:

```ruby
[1, 2, 3].count(&:odd?) > 1
```

With `many?`, we can make it simpler:

```ruby
[1, 2, 3].many?(&:odd?)
```

Pull Request on GitHub is available at https://github.com/ruby/ruby/pull/3785



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