1 files changed, 12 insertions, 5 deletions
diff --git a/activesupport/lib/active_support/core_ext/enumerable.rb b/activesupport/lib/active_support/core_ext/enumerable.rb
index 0d7d0159f9..92304a23f6 100644
--- a/activesupport/lib/active_support/core_ext/enumerable.rb
+++ b/activesupport/lib/active_support/core_ext/enumerable.rb
@@ -26,11 +26,18 @@ module Enumerable #:nodoc:
   #  payments.sum { |p| p.price * p.tax_rate }
   #  payments.sum(&:price)
   #
-  # This is instead of payments.inject(0) { |sum, p| sum + p.price }
-  def sum
-    inject(0) { |sum, element| sum + yield(element) }
+  # This is instead of payments.inject { |sum, p| sum + p.price }
+  #
+  # Also calculates sums without the use of a block:
+  #   [5, 15, 10].sum # => 30
+  def sum(&block)
+    if block_given?
+      map(&block).sum
+    else
+      inject { |sum, element| sum + element }
+    end
   end
-  
+
   # Convert an enumerable to a hash. Examples:
   # 
   #   people.index_by(&:login)
@@ -45,4 +52,4 @@ module Enumerable #:nodoc:
     end
   end
   
-end
-\ No newline at end of file
+end