Iterative Solution to the Problem of Determining Whether a Number is a Fibonacci Number or Not

iterative.rb

def is_fibonacci?(input_num)
  
  raise ArgumentError.new("Number must be greater than or equal to zero.") if input_num < 0
 
  # we start with these variable values to generate our array of fibonacci nums
  fibonacci_nums = [0,1]
  i = 1
  
  # we start with zero because this value is immediately changed in the first iteration and then incremented
  # it only has to be less than the input_num so the loop runs at least once
  current_fib_num = 0
  
  until current_fib_num > input_num
    next_fib_num = fibonacci_nums[i] + fibonacci_nums[i-1]
    fibonacci_nums.push(next_fib_num)
    i += 1
    current_fib_num = next_fib_num
  end
  
  # here's our iterative solution
  fibonacci_check = false
  fibonacci_nums.each do |val|
    if val.to_i == input_num
      fibonacci_check = true
    end
  end
  fibonacci_check
end