[ruby-core:109239] [Ruby master Feature#12648] `Enumerable#sort_by` with descending option

Issue #12648 has been updated by ttanimichi (Tsukuru Tanimichi).


It's a lot of work to write `sort_by { -1 * _1.created_at.to_f }` when the target objects are `Time` instances.

```ruby
['foo', 'bar', 'baz'].map { search(_1) }.flatten.sort_by { -1 * _1.created_at.to_f }

def search(query)
  client = Twitter::REST::Client.new do |config|
    config.consumer_key        = "YOUR_CONSUMER_KEY"
    config.consumer_secret     = "YOUR_CONSUMER_SECRET"
    config.access_token        = "YOUR_ACCESS_TOKEN"
    config.access_token_secret = "YOUR_ACCESS_SECRET"
  end
  
  client.search(query, result_type: "recent").take(10)
end
```

```
$ ruby -e "-1 * Time.now"
-e:1:in `*': Time can't be coerced into Integer (TypeError)
	from -e:1:in `<main>'
```

----------------------------------------
Feature #12648: `Enumerable#sort_by` with descending option
https://bugs.ruby-lang.org/issues/12648#change-98373

* Author: sawa (Tsuyoshi Sawada)
* Status: Open
* Priority: Normal
----------------------------------------
I would like to pass an optional argument to `Enumerable#sort_by` or `Enumerable#sort_by!` to allow descending sort. When the sort key is singular, this could be done by passing a single optinal boolean variable that represents ascending when `false` (default) and descending when `true`:

```ruby
[3, 1, 2].sort_by(&:itself)        # => [1, 2, 3]
[3, 1, 2].sort_by(false, &:itself) # => [1, 2, 3]
[3, 1, 2].sort_by(true, &:itself)  # => [3, 2, 1]
```

When there are multiple sort keys, corresponding numbers of arguments should be passed:

```ruby
[3, 1, 2, 0].sort_by{|e| [e % 2, e]}               # => [0, 2, 1, 3]
[3, 1, 2, 0].sort_by(false, false){|e| [e % 2, e]} # => [0, 2, 1, 3]
[3, 1, 2, 0].sort_by(false, true){|e| [e % 2, e]}  # => [2, 0, 3, 1]
[3, 1, 2, 0].sort_by(true, false){|e| [e % 2, e]}  # => [1, 3, 0, 2]
[3, 1, 2, 0].sort_by(true, true){|e| [e % 2, e]}   # => [3, 1, 2, 0]
```




-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:[e-mail]?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>