Procedural Ruby solution for the Spiral task

spiral.rb

def spiral(h, w, r, c)
  spiral = []

  step_counts = (1..Float::INFINITY).lazy.flat_map { |n| [n, n] }
  directions = [:up, :left, :down, :right].cycle

  while spiral.length < h * w
    spiral << (r - 1) * w + c if r.between?(1, h) && c.between?(1, w)

    if (current_step_count ||= 0).zero?
      current_step_count = step_counts.next
      current_direction = directions.next
    end

    case current_direction
      when :up then r -= 1
      when :down then r += 1
      when :left then c -= 1
      when :right then c += 1
    end

    current_step_count -= 1
  end

  spiral
end