Add Array#extract!

[bogdanvlviv]

The method removes and returns the elements for which the block returns a true value.
If no block is given, an Enumerator is returned instead.

numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
odd_numbers = numbers.extract! { |number| number.odd? } # => [1, 3, 5, 7, 9]
numbers # => [0, 2, 4, 6, 8]

Also, I added commit Use Array#extract! where possible in order to show that we can improve Rails code base by this method.

- nils, values = values.partition(&:nil?)
- ranges, values = values.partition { |v| v.is_a?(Range) }
+ nils = values.extract!(&:nil?)
+ ranges = values.extract! { |v| v.is_a?(Range) }

Looks more readable if use Array#extract!, doesn't it?

I know we try to omit adding new methods to ActiveSupport, but I think this one has a good chance to be added since we can apply it in Rails code base.
By the way, we already added Hash#extract!
https://github.com/rails/rails/blob/master/activesupport/lib/active_support/core_ext/hash/slice.rb#L41-L47

Post: https://gitlab.com/bogdanvlviv/posts/-/issues/14, https://bogdanvlviv.com/posts/ruby/rails/array-extract-to-activesupport-6-0.html

I have tried to add Active Support's Array#extract! as Array#extract to Ruby, see Feature #15831: "Add Array#extract, Hash#extract, and ENV.extract".

Thanks!

[rails-bot]

r? @schneems

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[rafaelfranca]

I'm ok with this one. @dhh what do you think of this name?

[dhh]

I like it! 👍

…

On Jun 14, 2018, at 23:07, Rafael França ***@***.***> wrote: I'm ok with this one. @dhh what do you think of this name? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or mute the thread.

[sikachu]

I honestly thought that this is what select! does, but apparently not. So, 👍from me too.

[matthewd]

FWIW, it would be named extract upstream... but as we already have Hash#extract!: 🤷🏻‍♂️

Also, I added commit Use Array#extract! where possible in order to show that we can improve Rails code base by this method.

💯. This was very helpful, thank you.

On the implementation: I'd like to avoid allocating the second array. What do you think of something like reject! { |el| extracted_elements << el if yield el } ?

Let's also avoid unless/else in favour of an early return; the double-negative of that else can be confusing, even though the code layout is nearly the same.

[bogdanvlviv]

Thanks for the review guys!

@matthewd I applied your suggestions in Refactor Array#extract!.

On the implementation: I'd like to avoid allocating the second array. What do you think of something like reject! { |el| extracted_elements << el if yield el } ?

I prepared benchmarks in order to ensure that the changes speed up the method: (Not sure that these benchmarks are completely right)

begin
  require "bundler/inline"
rescue LoadError => e
  $stderr.puts "Bundler version 1.10 or later is required. Please update
your Bundler"
  raise e
end

class Array
  def extract_v1!(&block)
    unless block_given?
      to_enum(:extract!) { size }
    else
      extracted_elements, other_elements = partition(&block)

      replace(other_elements)

      extracted_elements
    end
  end

  def extract_v2!
    return to_enum(:extract!) { size } unless block_given?

    extracted_elements = []

    reject! do |element|
      extracted_elements << element if yield(element)
    end

    extracted_elements
  end
end

gemfile(true) do
  source "https://rubygems.org"

  gem "benchmark-ips"
end

arrays_for_partition = Array.new(1000) { (0..10000).to_a }
arrays_for_extract_v1 = Array.new(1000) { (0..10000).to_a }
arrays_for_extract_v2 = Array.new(1000) { (0..10000).to_a }

Benchmark.ips do |x|
  x.report("Array#partition")  do
    arrays_for_partition.each do |numbers|
      odd_numbers, numbers = numbers.partition { |number| number.odd? }
      numbers
    end
  end

  x.report("Array#extract_v1!")  do
    arrays_for_extract_v1.each do |numbers|
      odd_numbers = numbers.extract_v1! { |number| number.odd? }
      numbers
    end
  end

  x.report("Array#extract_v2!")  do
    arrays_for_extract_v2.each do |numbers|
      odd_numbers = numbers.extract_v2! { |number| number.odd? }
      numbers
    end
  end

  x.compare!
end

The result of the benchmarks:

ruby -v
ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux]

Fetching gem metadata from https://rubygems.org/.
Resolving dependencies...
Using benchmark-ips 2.7.2
Using bundler 1.16.1
Warming up --------------------------------------
     Array#partition     1.000  i/100ms
   Array#extract_v1!     1.000  i/100ms
   Array#extract_v2!     1.000  i/100ms
Calculating -------------------------------------
     Array#partition      1.390  (± 0.0%) i/s -      7.000  in   5.044843s
   Array#extract_v1!      2.781  (± 0.0%) i/s -     14.000  in   5.050589s
   Array#extract_v2!      3.151  (± 0.0%) i/s -     16.000  in   5.080608s

Comparison:
   Array#extract_v2!:        3.2 i/s
   Array#extract_v1!:        2.8 i/s - 1.13x  slower
     Array#partition:        1.4 i/s - 2.27x  slower

Let's also avoid unless/else in favour of an early return; the double-negative of that else can be confusing, even though the code layout is nearly the same.

Yeah, It will be more readable and also using of early return would improve git diff
in some cases if we needed to change this method I think.

[sikachu]

I rerun the test case (twice, in the span of 6 days ..ha) and it is now passing. @matthewd @rafaelfranca would either of you mind merging this in if this is good to go?