0
@@ -23,21 +23,22 @@ module Enumerable
0
 
0
   # Calculates a sum from the elements. Examples:
0
   #
0
-  #   payments.sum { |p| p.price * p.tax_rate }
0
-  #   payments.sum(&:price)
0
+  #  payments.sum { |p| p.price * p.tax_rate }
0
+  #  payments.sum(&:price)
0
   #
0
-  # This is instead of
0
+  # The latter is a shortcut for:
0
   #
0
-  #   payments.inject { |sum, p| sum + p.price }
0
+  #  payments.inject { |sum, p| sum + p.price }
0
   #
0
-  # Also calculates sums without the use of a block:
0
+  # It can also calculate the sum without the use of a block.
0
   #
0
-  #   [5, 15, 10].sum # => 30
0
+  #  [5, 15, 10].sum # => 30
0
+  #  ["foo", "bar"].sum # => "foobar"
0
+  #  [[1, 2], [3, 1, 5]].sum => [1, 2, 3, 1, 5]
0
   #
0
-  # The default identity (sum of an empty list) is zero. 
0
-  # However, you can override this default:
0
+  # The default sum of an empty list is zero. You can override this default:
0
   #
0
-  #   [].sum(Payment.new(0)) { |i| i.amount } # => Payment.new(0)
0
+  #  [].sum(Payment.new(0)) { |i| i.amount } # => Payment.new(0)
0
   #
0
   def sum(identity = 0, &block)
0
     return identity unless size > 0