# Changes
## 4.0.0 summary
Add capabilities for sets using `subset`, `superset`, `joint`, `disjoint`.
Add capabilities for bags using `subbag`, `superbag`.
Add capabilities for readers using `read_to_string`.
Add quality by improving doc tests and unit tests.
Rename function macros from "fn" to "f" because it prevents keyword conflict.
Rename macros from `assume` to `assertable` because it's easier to understand.
Retire macros with `assure` because they're easy to implement by using if/then.
Upgrade Rust version from 2018 to 2021.