Pascal's Triangle Problem (recursive solution)

pascal_triangle.rb

class PascalTriangle
  def initialize
    @digits = []
  end

  def calculate_row(row)
    row = row.to_f
    0.upto(row) { |column| @digits << calculate_number(row, column).to_i }
    @digits
  end
  
  def calculate_number(row, column)
    r = row + 1
    if column == 0
      1
    else
      previous = calculate_number(row, column-1)
      previous * ((r - column) / column)
    end
  end
end

if __FILE__ == $0
  row = ARGV[0] || 5
  puts "Calculating Pascal's triangle row: #{row}"

  pc = PascalTriangle.new
  digits = pc.calculate_row(row)
  puts digits.join(', ')
end

Back at the beginning of this year @petesharum and I toyed around with the Pascal's Triangle problem. There was a post on HN. We had different approaches. Mine was slower because recursion is slower. I still liked what I came up with, though.