From: "matz (Yukihiro Matsumoto) via ruby-core" <ruby-core@...>
Date: 2025-07-10T08:45:25+00:00
Subject: [ruby-core:122710] [Ruby Feature#21455] Add a block argument to Array#join

Issue #21455 has been updated by matz (Yukihiro Matsumoto).

Status changed from Open to Rejected

It's fundamentally `join_map` we have rejected. Array#join should join, not mapping.
We are not going to add every enumerable method combined with map. `filter_map` is an exception.

Matz.


----------------------------------------
Feature #21455: Add a block argument to Array#join
https://bugs.ruby-lang.org/issues/21455#change-113987

* Author: leoarnold (Leo Arnold)
* Status: Rejected
----------------------------------------
I sometimes come across code like this where
the `Array#join` at the end can easily
be overlooked or stands out like a sore thumb:

```ruby
hex_string = string.bytes.map do |byte|
  format('%02X', byte)
end.join(' ')
```

It seems idiomatic and more succinct
to pass the block to `Array#join` directly:

```ruby
hex_string = string.bytes.join(' ') do |byte|
  format('%02X', byte)
end
```

Pull Request: https://github.com/ruby/ruby/pull/13731



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