| 15 | //! [optionalToString.sfinae] |
| 16 | template <typename T> |
| 17 | std::string optionalToString(T const& obj) { |
| 18 | auto maybe_toString = hana::sfinae([](auto&& x) -> decltype(x.toString()) { |
| 19 | return x.toString(); |
| 20 | }); |
| 21 | |
| 22 | return maybe_toString(obj).value_or("toString not defined"); |
| 23 | } |
| 24 | //! [optionalToString.sfinae] |
| 25 | |
| 26 | int main() { |