ruby loop refactor

Question

Hi All,

I have a loop that looks like this

def slow_loop(array)
 array.each_with_index do |item, i|
   next_item = array[i+1]
   if next_item && item.attribute == next_item.attribute
     do_something_with(next_item)
   end
 end
end

aside from changing the way do_something_with is called, how can i make this perform better?

thx,

-C

p.s.

Since it appears that this is an 'O(n)' operation, there is apparently no performance to be gained here, so the answer i chose is one that uses a ruby method that already encapsulates this operation. thanks for your help everybody

Answer 1

The performance of do_something_with is the main factor. Anything else would be micro-optimisation.

This should be O(n), you could work out a way to avoid the final check, but that's not going to be that costly in the grand scheme of things.

Answer 2

As others have mentioned you're not going to improve the performance much, but you could do this more cleanly like so:

array.each_cons(2) do |a, b|
  do_something_with(b) if a == b
end

Answer 3

I tend to agree with Garry on the optimization potential, but it can certainly be written more simply.

prev_attr = nil
my_array.each |item|
  do_something_with(item) if prev_attr and prev_attr == item.attribute
  prev_attr = item.attribute
end