| ID | Status | Owner | Desc |
|---|---|---|---|
| 21_1 | DONE | jinkaimori | split basic.hpp to avoid circular inclusion |
| 21_4 | DONE | jinkaimori | make behavior of as_int consistent with is_int |
| 21_5 | DONE | Da | string_u16 and string_u16_view |
| 21_6 | DONE | Da | string_u8 as an alias of string |
| 21_7 | DONE | Da | Use string_view to re-impl ==, !=, <, <= of string |