Add Array#split for dividing arrays into one or more subarrays by value or block

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@4208 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activesupport/CHANGELOG

@@ -1,3 +1,7 @@
+*SVN*
+
+* Add Array#split for dividing arrays into one or more subarrays by value or block. [Sam Stephenson]
+
 *1.3.1* (April 6th, 2005)
 
 * Clean paths inside of exception messages and traces. [Nicholas Seckar]

activesupport/lib/active_support/core_ext/array.rb

@@ -18,4 +18,23 @@ class Array #:nodoc:
     collection << fill_with until collection.size.modulo(number).zero?
     collection.each_slice(number, &block)
   end
+  
+  # Divide the array into one or more subarrays based on a delimiting +value+
+  # or the result of an optional block.
+  #
+  # ex.
+  #
+  #   [1, 2, 3, 4, 5].split(3)                # => [[1, 2], [4, 5]]
+  #   (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
 end

activesupport/test/core_ext/array_ext_test.rb

@@ -69,7 +69,28 @@ class ArrayExtGroupingTests < Test::Unit::TestCase
   end
 end
 
-class ArraToXmlTests < Test::Unit::TestCase
+class ArraySplitTests < Test::Unit::TestCase
+  def test_split_with_empty_array
+    assert_equal [[]], [].split(0)
+  end
+  
+  def test_split_with_argument
+    assert_equal [[1, 2], [4, 5]],  [1, 2, 3, 4, 5].split(3)
+    assert_equal [[1, 2, 3, 4, 5]], [1, 2, 3, 4, 5].split(0)
+  end
+  
+  def test_split_with_block
+    assert_equal [[1, 2], [4, 5], [7, 8], [10]], (1..10).to_a.split { |i| i % 3 == 0 }
+  end
+  
+  def test_split_with_edge_values
+    assert_equal [[], [2, 3, 4, 5]],  [1, 2, 3, 4, 5].split(1)
+    assert_equal [[1, 2, 3, 4], []],  [1, 2, 3, 4, 5].split(5)
+    assert_equal [[], [2, 3, 4], []], [1, 2, 3, 4, 5].split { |i| i == 1 || i == 5 }
+  end
+end
+
+class ArrayToXmlTests < Test::Unit::TestCase
   def test_to_xml
     xml = [
       { :name => "David", :age => 26 }, { :name => "Jason", :age => 31 }