cdef extern from "gsl/gsl_sf_lambert.h": double gsl_sf_lambert_W0(double x) int gsl_sf_lambert_W0_e(double x, gsl_sf_result * result) double gsl_sf_lambert_Wm1(double x) int gsl_sf_lambert_Wm1_e(double x, gsl_sf_result * result)
cdef extern from "gsl/gsl_sf_lambert.h": double gsl_sf_lambert_W0(double x) int gsl_sf_lambert_W0_e(double x, gsl_sf_result * result) double gsl_sf_lambert_Wm1(double x) int gsl_sf_lambert_Wm1_e(double x, gsl_sf_result * result)