Take items of original array instead of dup and delete

[krzysiek1507]

No description provided.

[kpheasey]

@krzysiek1507 This looks like it could be a a big performance boost, did you benchmark it?

[krzysiek1507]

# frozen_string_literal: true

require 'benchmark/ips'
require 'benchmark/memory'

def remaining_items(items)
  return unless items.size > 1

  items_copy = items.dup
  items_copy.delete_at(0)
  [items_copy.join('.').to_sym]
end

def remaining_items_opt(items)
  return unless items.size > 1

  [items[1..-1].join('.').to_sym]
end

items = ['a', 'b', 'c', 'd', 'e', 'f', 'g']

[:ips, :memory].each do |type|
  puts "#{type} benchmark:"
  puts

  Benchmark.public_send(type) do |x|
    x.report('original') { remaining_items items }
    x.report('patch') { remaining_items_opt items }

    x.compare!
  end
end

ruby 2.6.3p62 (2019-04-16 revision 67580) [x86_64-darwin18]
ips benchmark:

Warming up --------------------------------------
            original    56.524k i/100ms
               patch    63.157k i/100ms
Calculating -------------------------------------
            original    704.188k (± 3.3%) i/s -      3.561M in   5.063434s
               patch    809.425k (± 7.4%) i/s -      4.042M in   5.030366s

Comparison:
               patch:   809425.0 i/s
            original:   704188.2 i/s - 1.15x  slower

memory benchmark:

Calculating -------------------------------------
            original   464.000  memsize (     0.000  retained)
                         7.000  objects (     0.000  retained)
                         1.000  strings (     0.000  retained)
               patch   408.000  memsize (     0.000  retained)
                         7.000  objects (     0.000  retained)
                         1.000  strings (     0.000  retained)

Comparison:
               patch:        408 allocated
            original:        464 allocated - 1.14x more