Repeating Decimal

#!/usr/bin/env ruby
def repeating_decimal(a, b)
  x, r = a.divmod b
  qs = []
  rs = [r]
  loop {
    q, r = (r * 10).divmod b
    qs << q
    break if r == 0
    if i = rs.index(r)
      qs.insert i, '('
      qs << ')'
      break
    else
      rs << r
    end
  }
  "#{x}.#{qs.join ''}"
end

[*2..19].each {|e| puts "1/#{e} = #{repeating_decimal(1, e)}" }
[[2, 3], [9, 11], [7, 12], [22, 7]].each {|e1, e2|
  puts "#{e1}/#{e2} = #{repeating_decimal(e1, e2)}"
}