2 files changed, 14 insertions, 9 deletions
diff --git a/mrbgems/mruby-array-ext/mrblib/array.rb b/mrbgems/mruby-array-ext/mrblib/array.rb
index 1cd1eb643..fc5d87f2c 100644
--- a/mrbgems/mruby-array-ext/mrblib/array.rb
+++ b/mrbgems/mruby-array-ext/mrblib/array.rb
@@ -815,12 +815,11 @@ class Array
   #  a.permutation(0).to_a #=> [[]] # one permutation of length 0
   #  a.permutation(4).to_a #=> []   # no permutations of length 4
   def permutation(n=self.size, &block)
-    size = self.size
     return to_enum(:permutation, n) unless block
-    return if n > size
+    size = self.size
     if n == 0
-       yield []
-    else
+      yield []
+    elsif 0 < n && n <= size
       i = 0
       while i<size
         result = [self[i]]
@@ -835,6 +834,7 @@ class Array
         i += 1
       end
     end
+    self
   end
 
   ##
@@ -861,9 +861,8 @@ class Array
   #    a.combination(5).to_a  #=> []   # no combinations of length 5
 
   def combination(n, &block)
-    size = self.size
     return to_enum(:combination, n) unless block
-    return if n > size
+    size = self.size
     if n == 0
        yield []
     elsif n == 1
@@ -872,7 +871,7 @@ class Array
         yield [self[i]]
         i += 1
       end
-    else
+    elsif n <= size
       i = 0
       while i<size
         result = [self[i]]
@@ -882,6 +881,7 @@ class Array
         i += 1
       end
     end
+    self
   end
 
   ##
diff --git a/mrbgems/mruby-array-ext/test/array.rb b/mrbgems/mruby-array-ext/test/array.rb
index 4fad42518..a4e328b71 100644
--- a/mrbgems/mruby-array-ext/test/array.rb
+++ b/mrbgems/mruby-array-ext/test/array.rb
@@ -3,8 +3,11 @@
 
 def assert_permutation_combination(exp, receiver, meth, *args)
   act = []
-  receiver.__send__(meth, *args) { |v| act << v }
-  assert_equal(exp, act.sort)
+  ret = receiver.__send__(meth, *args) { |v| act << v }
+  assert "assert_#{meth}" do
+    assert_equal(exp, act.sort)
+    assert_same(receiver, ret)
+  end
 end
 
 def assert_permutation(exp, receiver, *args)
@@ -389,6 +392,7 @@ assert("Array#permutation") do
   assert_permutation([[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]], a, 3)
   assert_permutation([[]], a, 0)
   assert_permutation([], a, 4)
+  assert_permutation([], a, -1)
 end
 
 assert("Array#combination") do
@@ -399,6 +403,7 @@ assert("Array#combination") do
   assert_combination([[1,2,3,4]], a, 4)
   assert_combination([[]], a, 0)
   assert_combination([], a, 5)
+  assert_combination([], a, -1)
 end
 
 assert('Array#transpose') do