{
  "-a/x + b log(x) + c": "lambda x, a, b, c : -a/(x**1) + b*numpy.log(x) + c ; (1, 1, 1)",
  "-a/x^2 + b/x + c": "lambda x, a, b, c : -a/((x-0.27)**2) + b/(x-0.27) + c ; (1, 1, 1)",
  "2a/pi*arctan(x/a)": "lambda x, a: (4*a/numpy.pi)*numpy.arctan(x/a) ; (1)",
  "a+b*x^3": "lambda x, a : a*x**3 ; (1)",
  "carola": "lambda x, a, b, c : -a + b*numpy.log(x) + c*numpy.log(x)**3 ; (0.1, 0.01, 0.00001)"
}