15 ways to sum an array in Ruby

sum.rb

#!/usr/bin/env ruby

require 'test/unit'

class TestSums < Test::Unit::TestCase

  def setup
    @a = [2, 5, 18, 27]
    @sum = 0
  end

  def teardown
    assert_equal 52, @sum
  end

  def test1
    i = 0
    while i < @a.length
      @sum += @a[i]
      i = i + 1
    end
  end

  def test2
    i = 0
    begin
      @sum += @a[i]
      i = i + 1
    end while i < @a.length
  end

  def test3
    i = 0
    until i >= @a.length
      @sum += @a[i]
      i = i + 1
    end
  end

  def test4
    i = 0
    begin
      @sum += @a[i]
      i = i + 1
    end until i >= @a.length
  end

  def test5
    i = 0
    loop do
      @sum += @a[i]
      i = i + 1
      break if i >= @a.length
    end
  end

  def test6
    i = 0
    @a.length.times {
      @sum += @a[i]
      i = i + 1
    }
  end

  def test7
    for i in 0 .. @a.length - 1
      @sum += @a[i]
    end
  end

  def test8
    for i in @a
      @sum += i
    end
  end

  def test9
    i = @a.to_enum
    loop do
      @sum += i.next
    end
  end

  def test10
    d = @a.dup
    loop do
      i = d.shift
      break if i.nil?
      @sum += i
    end
  end

  def test11
    0.upto(@a.length - 1){ |i| @sum += @a[i] }
  end

  def test12
    @a.each { |i| @sum += i }
  end

  def test13
    @a.each_index { |i| @sum += @a[i] }
  end

  def test14
    @sum = @a.inject :+
  end

  def test15
    @sum = eval @a.join '+'
  end

end

@sum = @a.reduce(0) { |x, y| x + y }

@sum = @a.reduce(&:+)

@sum = @a.reduce(:+) # With base
@sum = @a.reduce(0, :+) # Without base
@sum = @a.sum # Ruby 2.4+