cats-eo-api-docs

Existential Optics for Scala 3 — the capability layer.

This root package hosts the '''capability traits''' (CanGet, CanGetOption, CanModify, CanFold, CanPut, CanPlace, CanReverseGet, CanTransform, CanModifyA, CanModifyF) that consuming code demands instead of concrete optic types: a method that reads takes a CanGet[S, A], never a Lens. Concrete optics (optics) are for construction and composition; capabilities are for use — one optic given per (S, A) pair keeps summoning unambiguous. recast re-brands an optic's phantom slots where soundness allows.

'''Where things live.''' This core module is deliberately macro-free: auto-derivation ships in the SEPARATE cats-eo-generics artifact (dev.constructive.eo.generics.{lens, prism, plate}) — do not look for a GenLens / Focus equivalent here. Coming from Monocle: Setter is optics.Modify (set is replace), Iso / Lens / Prism / Optional / Traversal / Getter / Fold keep their names, and Each / Index / At exist as plain constructor OBJECTS, not a typeclass zoo — optics.Each is optics.Traversal.each under the searched-for name, optics.Index focuses one positional/keyed slot (never inserts), and optics.At is the total Map lens to Option[V] (Some upserts, None deletes). They return ordinary optics; nothing to instance or derive. All composition, same-carrier or cross-family, is the one .andThen.