add expr_clone

  return expr->value;

}

ExprStorage expr_clone(const Expr* e) {

  ExprStorage copy;

  ExprStorage* c = ©

  while (e) {

    *c = ExprStorage(new Expr, bind(&expr_destroy, _1));

    (*c)->type = e->type;

    (*c)->value = e->value;

    if (e->list) {

      (*c)->list = expr_clone(e->list.get());

    }

    c = expr_get_next_storage(&**c);

    e = e->next.get();

  }

  return copy;

}

std::string expr_inspect(const Expr* expr) {

  std::stringstream s;

bool expr_is_value_quoted(const Expr* expr, const std::string& cmp);

const std::string& expr_get_value(const Expr* expr);

ExprStorage expr_clone(const Expr* e);

std::string expr_inspect(const Expr* expr);

} // namespace fviz