[ruby-core:88598] [Ruby trunk Feature#11076] Enumerable method count_by

Issue #11076 has been updated by djones (David Jones).


How about `tally`?

```ruby
array = ['aa', 'aA', 'bb', 'cc']
p array.tally(&:downcase) #=> {'aa'=>2,'bb'=>1,'cc'=>1}
```

`tally` describes quite well to me what this method does and avoids clashing with `group` or `count`.
`tally_by` might be worthy of consideration too.

## Definition of "Tally"

Current score or amount: _that takes his tally to 10 goals in 10 games._

  1. a record of a score or amount: _I kept a running tally of David's debt on a note above my desk._
  2. **a particular number taken as a group or unit to facilitate counting.**
  3. a mark registering a number or amount.
  4. an account kept by means of a tally.

----------------------------------------
Feature #11076: Enumerable method count_by
https://bugs.ruby-lang.org/issues/11076#change-73654

* Author: haraldb (Harald B旦ttiger)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
I very often use `Hash[array.group_by{|x|x}.map{|x,y|[x,y.size]}]`.

Would be nice with to have a method called `count_by`:

~~~ruby
array = ['aa', 'aA', 'bb', 'cc']
p array.count_by(&:downcase) #=> {'aa'=>2,'bb'=>1,'cc'=>1}
~~~



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