Convert a Ruby Integer into an Array of digits.

bench_integer_to_array.rb

##
# Looking at benchmark derivatives of:
# http://gistflow.com/posts/873-integer-to-array-of-digits-with-ruby
#

require 'benchmark'
require 'benchmark/ips'

module Test
  class << self
    def divmod(d)
      base, last_digit = d.divmod(10)
      digits = [last_digit]

      while base > 9 do
        base, last_digit = base.divmod(10)
        digits = digits.insert(0, last_digit)
      end

      digits.insert(0, base)
    end

    def divmod_reverse(d)
      digits = []

      while d > 9 do
        d, last_digit = d.divmod(10)
        digits << last_digit
      end

      digits << d
      digits.reverse
    end

    def mikdie(d)
      digits = []

      until d == 0 do
        d, last_digit = d.divmod(10)
        digits << last_digit
      end

      digits.reverse
    end

    def each_char_map(d)
      d.to_s.each_char.map(&:to_i)
    end

    def chars_map(d)
      d.to_s.chars.map(&:to_i)
    end

    def chars_map_bang(d)
      d.to_s.chars.map!(&:to_i)
    end
  end
end

Benchmark.ips do |r|
  N = 123_456_789_123_456_789_123_456_789

  Test.methods(false).each do |method|
    r.report(method.to_s) do
      Test.send(method, N)
    end
  end
end

# >>  Calculating -------------------------------------
# >>                divmod      7915 i/100ms
# >>        divmod_reverse      9702 i/100ms
# >>                mikdie      9684 i/100ms
# >>         each_char_map      9983 i/100ms
# >>             chars_map     10446 i/100ms
# >>        chars_map_bang     11363 i/100ms
# >>  -------------------------------------------------
# >>                divmod   105944.7 (±26.7%) i/s -     498645 in   5.034317s
# >>        divmod_reverse   142615.2 (±41.0%) i/s -     591822 in   5.002818s
# >>                mikdie   142368.9 (±40.8%) i/s -     600408 in   5.048888s
# >>         each_char_map   128670.1 (±24.5%) i/s -     598980 in   5.015994s
# >>             chars_map   137758.9 (±27.9%) i/s -     637206 in   5.051835s
# >>        chars_map_bang   148910.0 (±23.9%) i/s -     693143 in   5.001251s