kernel: Colour and Subject shared vocabulary

The six liturgical colours and the Lord/BVM/saint/temporal distinction are
common to both Roman forms, so they are shared closed variants rather than
rite-parametric. Subject is so named because class is an OCaml keyword.

1 files changed, 14 insertions, 0 deletions

diff --git a/lib/kernel/colour.ml b/lib/kernel/colour.ml
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+(* Liturgical colours. Shared across Roman rites (spec §2.1): not
+   rite-parametric, because EF and OF use the same six. *)
+type t = White | Red | Green | Violet | Rose | Black [@@deriving sexp]
+
+let all = [ White; Red; Green; Violet; Rose; Black ]
+
+let to_string = function
+  | White -> "white" | Red -> "red" | Green -> "green"
+  | Violet -> "violet" | Rose -> "rose" | Black -> "black"
+
+let of_string = function
+  | "white" -> Some White | "red" -> Some Red | "green" -> Some Green
+  | "violet" -> Some Violet | "rose" -> Some Rose | "black" -> Some Black
+  | _ -> None