const struct layer *layer = mt->layers[l];
const struct variable *var = layer->factor_vars[ws->control_idx[l]];
ds_put_cstr (&dss, var_get_name (var));
const struct layer *layer = mt->layers[l];
const struct variable *var = layer->factor_vars[ws->control_idx[l]];
ds_put_cstr (&dss, var_get_name (var));