code: def lerfcc(x):
      
      z = abs(x)
      t = 1.0 / (1.0+0.5*z)
      ans = t * math.exp(-z*z-1.26551223 + t*(1.00002368+t*(0.37409196+t*(0.09678418+t*(-0.18628806+t*(0.27886807+t*(-1.13520398+t*(1.48851587+t*(-0.82215223+t*0.17087277)))))))))
      if x >= 0:
          return ans
      else:
          return 2.0 - ans
docs: Returns the complementary error function erfc(x) with fractional
  error everywhere less than 1.2e-7.  Adapted from Numerical Recipies.
  
  Usage:   lerfcc(x)