Clarify Array#in_groups_of implementation, don't dup unless needed, only require enumerator once.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@8161 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activesupport/lib/active_support/core_ext/array/grouping.rb

+require 'enumerator'
+
 module ActiveSupport #:nodoc:
   module CoreExtensions #:nodoc:
     module Array #:nodoc:
@@ -21,14 +23,23 @@ module Grouping
         #   ["1", "2"]
         #   ["3"]
         def in_groups_of(number, fill_with = nil, &block)
-          require 'enumerator'
-          collection = dup
-          collection << fill_with until collection.size.modulo(number).zero? unless fill_with == false
-          grouped_collection = [] unless block_given?
-          collection.each_slice(number) do |group|
-            block_given? ? yield(group) : grouped_collection << group
+          if fill_with == false
+            collection = self
+          else
+            # size % number gives how many extra we have;
+            # subtracting from number gives how many to add;
+            # modulo number ensures we don't add group of just fill.
+            padding = (number - size % number) % number
+            collection = dup.concat([fill_with] * padding)
+          end
+
+          if block_given?
+            collection.each_slice(number, &block)
+          else
+            returning [] do |groups|
+              collection.each_slice(number) { |group| groups << group }
+            end
           end
-          grouped_collection unless block_given?
         end
 
         # Divide the array into one or more subarrays based on a delimiting +value+
@@ -40,12 +51,14 @@ def in_groups_of(number, fill_with = nil, &block)
         #   (1..10).to_a.split { |i| i % 3 == 0 }   # => [[1, 2], [4, 5], [7, 8], [10]]
         def split(value = nil, &block)
           block ||= Proc.new { |e| e == value }
+
           inject([[]]) do |results, element|
             if block.call(element)
               results << []
             else
               results.last << element
             end
+
             results
           end
         end