double cauchy (double x, void *p) { return gsl_ran_cauchy_pdf (x, *(double*)p); }
double test_cauchy_pdf (double x) { return gsl_ran_cauchy_pdf (x, 2.0); }
double test_levy1a_pdf (double x) { return gsl_ran_cauchy_pdf (x, 5.0); }
double test_levy_skew1b_pdf (double x) { return gsl_ran_cauchy_pdf (x, 5.0); }
double distr_proposal(double x) { return gsl_ran_cauchy_pdf(x, 1); }