code: def recomb_probability(cM, method="kosambi"):
      
      assert method in ("kosambi", "haldane")
      d = cM / 100.
      if method == "kosambi":
          e4d = exp(4 * d)
          return (e4d - 1) / (e4d + 1) / 2
      elif method == "haldane":
          return (1 - exp(-2 * d)) / 2
docs: <http://statgen.ncsu.edu/qtlcart/manual/node46.html>
  
      >>> recomb_probability(1)
      0.009998666879965463
      >>> recomb_probability(100)
      0.48201379003790845
      >>> recomb_probability(10000)
      0.5