double gsl_sf_lambert_Wm1(double x) { EVAL_RESULT(gsl_sf_lambert_Wm1_e(x, &result)); }
static VALUE Lambert_Wm1_e(VALUE self, VALUE x) { int ret; gsl_sf_result r; ret = gsl_sf_lambert_Wm1_e(NUM2DBL(x), &r); return RESULT(&r); }