From 7bc3c79cb1a6a5ac71f01d02ef78f3541471abb9 Mon Sep 17 00:00:00 2001
From: Grzegorz Jakubiak <grzegorz.jakubiak@outlook.com>
Date: Sat, 15 Feb 2025 23:50:53 +0100
Subject: [PATCH] Introduce Hash#keys_to_set

---
 lib/set.rb       | 13 +++++++++++++
 test/test_set.rb | 10 ++++++++++
 2 files changed, 23 insertions(+)

diff --git a/lib/set.rb b/lib/set.rb
index 86bbe40..f93c193 100644
--- a/lib/set.rb
+++ b/lib/set.rb
@@ -852,4 +852,17 @@ def to_set(klass = Set, *args, &block)
   end unless method_defined?(:to_set)
 end
 
+class Hash
+  # Returns a new Set containing keys from the Hash
+  #
+  #   h = {a: 1, b: 3}
+  #   h.keys_to_set #=> Set[:a, :b]
+  #
+  def keys_to_set
+    set = Set.new
+    set.instance_variable_set(:@hash, transform_values { true })
+    set
+  end
+end
+
 autoload :SortedSet, "#{__dir__}/set/sorted_set"
diff --git a/test/test_set.rb b/test/test_set.rb
index 5659460..7165a62 100644
--- a/test/test_set.rb
+++ b/test/test_set.rb
@@ -857,6 +857,16 @@ def test_to_set
   end
 end
 
+class TC_Hash < Test::Unit::TestCase
+  def test_keys_to_set
+    h = {a: 2, b: 1, c: 37}
+    set = h.keys_to_set
+    expected = Set.new(h.keys)
+
+    assert_equal(set, expected)
+  end
+end
+
 class TC_Set_Builtin < Test::Unit::TestCase
   private def should_omit?
     (RUBY_VERSION.scan(/\d+/).map(&:to_i) <=> [3, 2]) < 0 ||