The suggested alternative for FlipFlop is wrong

[kke]

The FlipFlop cop documentation from 684d835 states:

      # @example
      #   # bad
      #   (1..20).each do |x|
      #     puts x if (x == 5) .. (x == 10)
      #   end
      #
      #   # good
      #   (1..20).each do |x|
      #     puts x if (x >= 5) && (x <= 10)
      #   end

The suggested better alternative however does something completely different than the bad example for a different kind of dataset, for example:

irb(main):084:0> [5,20,15,10,5].each { |x| puts x if (x >= 5) && (x <= 10) }
5
10
5
irb(main):085:0> [5,20,15,10,5].each { |x| puts x if (x == 5)..(x == 10) }
5
20
15
10
5

Maybe the examples should be something like:

# bad
[4, 3, 2, 1, 2, 3, 4].each do |x|
  puts x if (x==3)..(x==2)
end

And:

# good
output_enabled = false
[4, 3, 2, 1, 2, 3, 4].each do |x|
  output_enabled = true if x == 3
  puts x if output_enabled
  output_enabled = false if x == 2
end

The good one does not look that hot either, but maybe someone can come up with a prettier solution.

[andriimosin]

The 'good' example is definitely wrong here, but FlipFlop is really weird and rare operator and I'm not even sure what alternative can be put in a 'good' example.

Your suggested alternative is correct but in fact, it's just an algorithm rather than a good practice example. I'm not sure that it's the best option to suggest here.

Maybe it will sound too much, but maybe it's not be a bad idea to just suggest not to use it at all? I mean without 'good' example.

Check out this article about how rare this operator is:

about 1 in every 23 million lines of Ruby code, or 1-in-10 million to round to an order of magnitude

[koic]

flip-flop is deprecated since Ruby 2.6.0.
https://github.com/ruby/ruby/blob/v2_6_0/NEWS#language-changes

I didn't improve the good example code, but I updated by #6635 why flip-flop isn't good.

[kke]

Good riddance

[koic]

Thank you. I will close this issue, but If you have good example code please open a PR.