* array.c (rb_ary_permutation): Support for Array#permutation.size

  [Feature #6636]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@37501 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 13 insertions, 0 deletions

diff --git a/test/ruby/test_enumerator.rb b/test/ruby/test_enumerator.rb
index c276455a01..a4222f2ac0 100644
--- a/test/ruby/test_enumerator.rb
+++ b/test/ruby/test_enumerator.rb
@@ -429,5 +429,18 @@ class TestEnumerator < Test::Unit::TestCase
     end
   end
 
+  def check_consistency_for_combinatorics(method)
+    [ [], [:a, :b, :c, :d, :e] ].product([-2, 0, 2, 5, 6]) do |array, arg|
+      assert_equal array.send(method, arg).to_a.size, array.send(method, arg).size,
+        "inconsistent size for #{array}.#{method}(#{arg})"
+    end
+  end
+
+  def test_size_for_array_combinatorics
+    check_consistency_for_combinatorics(:permutation)
+    assert_equal 24, [0, 1, 2, 4].permutation.size
+    assert_equal 2933197128679486453788761052665610240000000,
+      (1..42).to_a.permutation(30).size # 1.upto(42).inject(:*) / 1.upto(12).inject(:*)
+  end
 end