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]```

Avoid allocating the second array by using `Array#reject!` instead of`Enumerable#partition` in `Array#extract!`.There are benchmarks in order to ensure that the changes speed up the method:```begin  require "bundler/inline"rescue LoadError => e  $stderr.puts "Bundler version 1.10 or later is required. Please updateyour Bundler"  raise eendclass 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  endendgemfile(true) do  source "https://rubygems.org"  gem "benchmark-ips"endarrays_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 -vruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux]``````Fetching gem metadata fromhttps://rubygems.org/.Resolving dependencies...Using benchmark-ips 2.7.2Using bundler 1.16.1Warming up --------------------------------------     Array#partition     1.000  i/100ms   Array#extract_v1!     1.000  i/100ms   Array#extract_v2!     1.000  i/100msCalculating -------------------------------------     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   5.080608sComparison:   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```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.Also using of early return would improve `git diff`if we needed to change this method.