array iteration problem

rb_array_iterate.rb

def add1(arr, val, n)
  # how many times are we going to increment
  increment_count = n == 0 ? arr.length : n.abs
  # are we going up or down the array
  indices = n < 0 ? (-1..-arr.length) : (0...arr.length)
  # iterate and update the array in place
  indices.each do |index|
    arr[index] = arr[index] + 1 if val == arr[index]

    break if (increment_count -= 1) == 0
  end
  arr
end