Optimize Range#sum to use arithmetic progression when a block is not …

…given [#2489]. Signed-off-by: Pratik Naik <pratiknaik@gmail.com>
rails · Aug 9, 2009 · 1bd4d1c · 1bd4d1c · marcandre · Aug 9, 2009
1 parent d811864
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diff --git a/activesupport/lib/active_support/core_ext/enumerable.rb b/activesupport/lib/active_support/core_ext/enumerable.rb
@@ -111,3 +111,12 @@ def none?(&block)
     !any?(&block)
   end unless [].respond_to?(:none?)
 end
+
+class Range #:nodoc:
+  # Optimize range sum to use arithmetic progression if a block is not given.
+  def sum(identity=0, &block)
+    return super if block_given?
+    actual_last = exclude_end? ? (last - 1) : last
+    (actual_last - first + 1) * (actual_last + first) / 2
+  end
+end
diff --git a/activesupport/test/core_ext/enumerable_test.rb b/activesupport/test/core_ext/enumerable_test.rb
@@ -61,7 +61,9 @@ def test_empty_sums
   end
 
   def test_enumerable_sums
+    assert_equal 20, (1..4).sum { |i| i * 2 }
     assert_equal 10, (1..4).sum
+    assert_equal 6, (1...4).sum
   end
 
   def test_each_with_object