From c703c39ae7f5f5e72f0458383a80395d773aed5c Mon Sep 17 00:00:00 2001
From: "T.J. Schuck" <tj@getharvest.com>
Date: Wed, 18 Nov 2015 17:40:58 -0500
Subject: Change Enumerable#sum to use inject(:sym) specification
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Not only does this make for simpler, more obvious code, it's also more performant:

    require 'benchmark/ips'

    module Enumerable
      def old_sum(identity = 0, &block)
        if block_given?
          map(&block).old_sum(identity)
        else
          inject { |sum, element| sum + element } || identity
        end
      end

      def new_sum(identity = 0, &block)
        if block_given?
          map(&block).new_sum(identity)
        else
          inject(:+) || identity
        end
      end
    end

    summable = (1..100).to_a # sum is 5050

    Benchmark.ips do |x|
      x.report("old_sum") { summable.old_sum }
      x.report("new_sum") { summable.new_sum }
      x.compare!
    end

    # Calculating -------------------------------------
    #              old_sum    10.674k i/100ms
    #              new_sum    14.542k i/100ms
    # -------------------------------------------------
    #              old_sum    117.350k (± 7.1%) i/s -    587.070k
    #              new_sum    154.712k (± 3.8%) i/s -    785.268k
    #
    # Comparison:
    #              new_sum:   154712.1 i/s
    #              old_sum:   117350.0 i/s - 1.32x slower

More benchmarks [here](https://gist.github.com/tjschuck/b3fe4e8c812712376648), including summing strings and passing blocks.  The performance gains are less for those, but this version still always wins.
---
 activesupport/lib/active_support/core_ext/enumerable.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'activesupport')

diff --git a/activesupport/lib/active_support/core_ext/enumerable.rb b/activesupport/lib/active_support/core_ext/enumerable.rb
index fc7531d088..8a74ad4d66 100644
--- a/activesupport/lib/active_support/core_ext/enumerable.rb
+++ b/activesupport/lib/active_support/core_ext/enumerable.rb
@@ -21,7 +21,7 @@ module Enumerable
     if block_given?
       map(&block).sum(identity)
     else
-      inject { |sum, element| sum + element } || identity
+      inject(:+) || identity
     end
   end
 
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