From: sawadatsuyoshi@...
Date: 2020-06-27T01:55:58+00:00
Subject: [ruby-core:98971] [Ruby master Feature#16993] Sets: from hash keys	using Hash#key_set

Issue #16993 has been updated by sawa (Tsuyoshi Sawada).


Would

```ruby
Set.new(h.each_key)
```

not work?

----------------------------------------
Feature #16993: Sets: from hash keys using Hash#key_set
https://bugs.ruby-lang.org/issues/16993#change-86352

* Author: marcandre (Marc-Andre Lafortune)
* Status: Open
* Priority: Normal
----------------------------------------
To create a set from hash keys currently implies a temporary array for all keys, rehashing all those keys and rebuilding a hash. Instead, the hash could be copied and its values set to `true`.

```ruby
h = {a: 1}
# Now:
Set.new(h.keys) # => Set[:a]
# After
h.key_set # => Set[:a], efficiently.
```




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