From fd0eaaa407fb8fd704967be2734c1b094ac630d9 Mon Sep 17 00:00:00 2001
From: David Heinemeier Hansson <david@loudthinking.com>
Date: Sat, 24 Jun 2006 16:14:59 +0000
Subject: Added Enumerable#sum for calculating a sum from the elements [DHH]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@4489 5ecf4fe2-1ee6-0310-87b1-e25e094e27de
---
 activesupport/lib/active_support/core_ext/enumerable.rb | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

(limited to 'activesupport/lib')

diff --git a/activesupport/lib/active_support/core_ext/enumerable.rb b/activesupport/lib/active_support/core_ext/enumerable.rb
index 5c556ff98d..4de520f4ed 100644
--- a/activesupport/lib/active_support/core_ext/enumerable.rb
+++ b/activesupport/lib/active_support/core_ext/enumerable.rb
@@ -1,3 +1,5 @@
+require File.dirname(__FILE__) + '/enumerable/injections'
+
 module Enumerable #:nodoc:
   # Collect an enumerable into sets, grouped by the result of a block. Useful,
   # for example, for grouping records by date.
@@ -20,4 +22,14 @@ module Enumerable #:nodoc:
       groups
     end
   end 
-end
+
+  # Calculates a sum from the elements. Examples:
+  #
+  #  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) }
+  end
+end
\ No newline at end of file
-- 
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