kernel: Vocab, Celebration and Temporal parametric types

Rite specificity is carried by type parameters plus a vocab record of
operations rather than by functors: the same guarantee that a rite cannot name
another rite's season, without threading module plumbing through every kernel
module. Celebration takes only the rank parameter, since it has no season
field and OCaml rejects a type variable that appears in no field.

1 files changed, 20 insertions, 0 deletions

diff --git a/lib/kernel/celebration.ml b/lib/kernel/celebration.ml
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+++ b/lib/kernel/celebration.ml
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+open Sexplib0.Sexp_conv
+
+(* A celebration as computed or as loaded from a layer.
+
+   One type parameter, not two: the record has no season field, and OCaml
+   rejects a type variable that appears in no field. *)
+type 'r t = {
+  slug : Slug.t;
+  names : Names.t;
+  rank : 'r;
+  colour : Colour.t;
+  subject : Subject.t;
+  citations : Citation.t list;
+  layer : string;  (** provenance: "temporal", a layer id, or an overlay id *)
+}
+[@@deriving sexp]
+
+let make ~slug ?(names = Names.empty) ~rank ~colour ?(subject = Subject.Temporal)
+    ?(citations = []) ~layer () =
+  { slug; names; rank; colour; subject; citations; layer }