Implement Hash#pick

hash.c

@@ -1348,6 +1348,30 @@ rb_hash_values_at(int argc, VALUE *argv, VALUE hash)
     return result;
 }
 
+/*
+ * call-seq:
+ *   hsh.pick(key, ...)   -> Hash
+ *
+ * Return a key-value pair associated with given keys. 
+ *
+ * { :a => 1, 2 => "2", "c" => true }.pick(:a, 2) # => { :a => 1, 2 => "2" }
+ * { :a => 1, 2 => "2", "c" => true }.pick("c", 10000) # => { "c" => true, 10000 => nil }
+ */
+
+VALUE
+rb_hash_pick(int argc, VALUE *argv, VALUE self){
+  int i;
+  VALUE result, value;
+  result = rb_hash_new();
+
+  for(i=0; i < argc; i++){
+    value = rb_hash_aref(self, argv[i]);
+    rb_hash_aset(result, argv[i], value);
+  }
+
+  return result;
+}
+
 /*
  * call-seq:
  *   hsh.fetch_values(key, ...)                 -> array
@@ -4485,6 +4509,7 @@ Init_Hash(void)
     rb_define_method(rb_cHash, "keys", rb_hash_keys, 0);
     rb_define_method(rb_cHash, "values", rb_hash_values, 0);
     rb_define_method(rb_cHash, "values_at", rb_hash_values_at, -1);
+    rb_define_method(rb_cHash, "pick", rb_hash_pick, -1);
     rb_define_method(rb_cHash, "fetch_values", rb_hash_fetch_values, -1);
 
     rb_define_method(rb_cHash, "shift", rb_hash_shift, 0);

test/ruby/test_hash.rb

@@ -572,6 +572,21 @@ def test_values_at
     assert_equal ['three', nil, 'one', 'nil'], res
   end
 
+  def test_pick
+    res = @h.pick()
+    assert_equal({}, res)
+
+    res = @h.pick(1,2)
+    assert_equal({1 => "one", 2 => "two"}, res)
+
+    res = @h.pick(1,2,1000)
+    assert_equal({1 => "one", 2 => "two", 1000 => nil}, res)
+
+    h = { a: 10 } 
+    h.default= "default"
+    assert_equal({1000 => "default"}, h.pick(1000))
+  end
+
   def test_fetch_values
     res = @h.fetch_values
     assert_equal(0, res.length)