glass	2017-10-21 15:08:33 +0900 (Sat, 21 Oct 2017)

  New Revision: 60229

  https://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=60229

  Log:
    hash.c: Add Hash#slice
    
    * hash.c (rb_hash_slice): add Hash#slice [Feature #8499]

  Modified files:
    trunk/hash.c
    trunk/test/ruby/test_hash.rb
Index: hash.c
===================================================================
--- hash.c	(revision 60228)
+++ hash.c	(revision 60229)
@@ -1325,6 +1325,38 @@ rb_hash_reject(VALUE hash) https://github.com/ruby/ruby/blob/trunk/hash.c#L1325
 }
 
 /*
+ *  call-seq:
+ *     hsh.slice -> a_hash
+ *
+ *  Slices a hash to include only the given keys.
+ *  Returns a hash containing the given keys.
+ *
+ *     h = { "a" => 100, "b" => 200, "c" => 300 }
+ *     h.slice("a")  #=> {"a" => 100}
+ */
+
+static VALUE
+rb_hash_slice(int argc, VALUE *argv, VALUE hash)
+{
+    int i;
+    VALUE key, value, result;
+
+    if (argc == 0 || RHASH_EMPTY_P(hash)) {
+	return rb_hash_new();
+    }
+    result = rb_hash_new_with_size(argc);
+
+    for (i = 0; i < argc; i++) {
+	key = argv[i];
+	value = rb_hash_lookup2(hash, key, Qundef);
+	if (value != Qundef)
+	    rb_hash_aset(result, key, value);
+    }
+
+    return result;
+}
+
+/*
  * call-seq:
  *   hsh.values_at(key, ...)   -> array
  *
@@ -4585,6 +4617,7 @@ Init_Hash(void) https://github.com/ruby/ruby/blob/trunk/hash.c#L4617
     rb_define_method(rb_cHash, "select!", rb_hash_select_bang, 0);
     rb_define_method(rb_cHash, "reject", rb_hash_reject, 0);
     rb_define_method(rb_cHash, "reject!", rb_hash_reject_bang, 0);
+    rb_define_method(rb_cHash, "slice", rb_hash_slice, -1);
     rb_define_method(rb_cHash, "clear", rb_hash_clear, 0);
     rb_define_method(rb_cHash, "invert", rb_hash_invert, 0);
     rb_define_method(rb_cHash, "update", rb_hash_update, 1);
Index: test/ruby/test_hash.rb
===================================================================
--- test/ruby/test_hash.rb	(revision 60228)
+++ test/ruby/test_hash.rb	(revision 60229)
@@ -1006,6 +1006,14 @@ class TestHash < Test::Unit::TestCase https://github.com/ruby/ruby/blob/trunk/test/ruby/test_hash.rb#L1006
     assert_equal(nil, h.select!{true})
   end
 
+  def test_slice
+    h = @cls[1=>2,3=>4,5=>6]
+    assert_equal({1=>2, 3=>4}, h.slice(1, 3))
+    assert_equal({}, h.slice(7))
+    assert_equal({}, h.slice)
+    assert_equal({}, {}.slice)
+  end
+
   def test_clear2
     assert_equal({}, @cls[1=>2,3=>4,5=>6].clear)
     h = @cls[1=>2,3=>4,5=>6]

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