eo
eo is a sister project: an existential optics library for Scala 3, built on cats.
One Optic[S, T, A, B, F] trait, parameterised over a carrier F[_, _], unifies every optic
family. A function can demand a capability (CanModify[T, String]) instead of a concrete
type, and the caller supplies the optic that proves it — the same move Fixed makes for every
value in the language.