diff --git a/bootstrap/bin/hocc/code.ml b/bootstrap/bin/hocc/code.ml
index b0c5a316..c08ba173 100644
--- a/bootstrap/bin/hocc/code.ml
+++ b/bootstrap/bin/hocc/code.ml
@@ -124,22 +124,31 @@ let hmi_template = {|{
             include IdentifiableIntf.S with type t := t
           }
 
-        Prec = {
+        PrecSet = {
             type t: t = {
-                index: uns # Index in `precs` array.
-                name: string
+                index: uns # Index in `precSets` array.
+                names: array string
                 assoc: option Assoc.t
-                doms: Ordset.t uns Uns.cmper_witness # Indices in `precs` array of dominator
-                                                     # precedences.
+                doms: Ordset.t uns Uns.cmper_witness # Indices in `precSets` array of dominator
+                                                     # precedence sets.
               }
 
             include IdentifiableIntf.S with type t := t
           }
 
-        precs: array Prec.t
-          [@@doc "Array of precedences, where each element's `index` field corresponds to the
+        precSets: array PrecSet.t
+          [@@doc "Array of precedence sets, where each element's `index` field corresponds to the
           element's array index."]
 
+        Prec = {
+            type t: t = {
+                name_index: uns # Index of precedence name in precedence set.
+                prec_set_index: uns # Index of precedence set in `precSets`.
+              }
+
+            include IdentifiableIntf.S with type t := t
+          }
+
         Prod = {
             type t: t = {
                 index: uns # Index in `prods` array.
diff --git a/bootstrap/bin/hocc/description.ml b/bootstrap/bin/hocc/description.ml
index 2e78d1a5..0f2e92cb 100644
--- a/bootstrap/bin/hocc/description.ml
+++ b/bootstrap/bin/hocc/description.ml
@@ -72,7 +72,7 @@ let generate_description conf io description Spec.{algorithm; precs; symbols; pr
       match do_pp_prec, prec with
       | false, _
       | _, None -> formatter
-      | true, Some {name; _} -> formatter |> Fmt.fmt " " |> pp_prec name
+      | true, Some prec -> formatter |> Fmt.fmt " " |> pp_prec (Prec.name prec)
     )
   end in
   let pp_lr0item lr0item formatter = begin
@@ -121,7 +121,7 @@ let generate_description conf io description Spec.{algorithm; precs; symbols; pr
       match do_pp_prec, prec with
       | false, _
       | _, None -> formatter
-      | true, Some {name; _} -> formatter |> Fmt.fmt " " |> pp_prec name
+      | true, Some prec -> formatter |> Fmt.fmt " " |> pp_prec (Prec.name prec)
     )
   end in
   let pp_state_index state_index formatter = begin
@@ -136,7 +136,7 @@ let generate_description conf io description Spec.{algorithm; precs; symbols; pr
       let symbol = Symbols.symbol_of_symbol_index symbol_index symbols in
       match symbol.prec with
       | None -> formatter
-      | Some Prec.{name; _} -> formatter |> Fmt.fmt " " |> pp_prec name
+      | Some prec -> formatter |> Fmt.fmt " " |> pp_prec (Prec.name prec)
     end in
     let pp_reduce_prec Prod.{lhs_index; prec; _} formatter = begin
       match prec with
@@ -241,7 +241,7 @@ let generate_description conf io description Spec.{algorithm; precs; symbols; pr
         | Some Right -> "right"
       )
       |> (fun formatter ->
-        List.fold ~init:formatter ~f:(fun formatter name ->
+        Array.fold ~init:formatter ~f:(fun formatter name ->
           formatter
           |> Fmt.fmt " " |> html "<a id=\"prec-" |> html name |> html "\">"
           |> Fmt.fmt name
@@ -254,7 +254,7 @@ let generate_description conf io description Spec.{algorithm; precs; symbols; pr
         | false -> begin
             let _, formatter = Ordset.fold ~init:(true, formatter)
               ~f:(fun (first, formatter) prec_ind ->
-                List.fold ~init:(first, formatter) ~f:(fun (first, formatter) name ->
+                Array.fold ~init:(first, formatter) ~f:(fun (first, formatter) name ->
                   let formatter =
                     formatter
                     |> Fmt.fmt (match first with
@@ -303,7 +303,7 @@ let generate_description conf io description Spec.{algorithm; precs; symbols; pr
             |> (fun formatter ->
               match prec with
               | None -> formatter
-              | Some {name; _} -> formatter |> Fmt.fmt " " |> pp_prec name
+              | Some prec -> formatter |> Fmt.fmt " " |> pp_prec (Prec.name prec)
             )
             |> Fmt.fmt "\n"
             |> html "        <ul type=none>\n"
diff --git a/bootstrap/bin/hocc/lr1Item.ml b/bootstrap/bin/hocc/lr1Item.ml
index 7f3f421b..4076a5e9 100644
--- a/bootstrap/bin/hocc/lr1Item.ml
+++ b/bootstrap/bin/hocc/lr1Item.ml
@@ -43,7 +43,7 @@ module T = struct
     |> (fun formatter ->
       match prec with
       | None -> formatter
-      | Some {name; _} -> formatter |> Fmt.fmt " prec " |> String.fmt name
+      | Some prec -> formatter |> Fmt.fmt " " |> Prec.pp_hr prec
     )
 end
 include T
diff --git a/bootstrap/bin/hocc/prec.ml b/bootstrap/bin/hocc/prec.ml
index 11818b14..ac800a1a 100644
--- a/bootstrap/bin/hocc/prec.ml
+++ b/bootstrap/bin/hocc/prec.ml
@@ -1,22 +1,26 @@
 open Basis
 open! Basis.Rudiments
 
+module Index = Uns
 type t = {
-  name: string;
+  name_index: Index.t;
   prec_set: PrecSet.t;
 }
 
-let pp {name; prec_set} formatter =
+let name {name_index; prec_set={names; _}} =
+  Array.get name_index names
+
+let pp {name_index; prec_set} formatter =
   formatter
-  |> Fmt.fmt "{name=" |> String.pp name
+  |> Fmt.fmt "{name_index=" |> Index.pp name_index
   |> Fmt.fmt "; prec_set=" |> PrecSet.pp prec_set
 
-let pp_hr {name; _} formatter =
+let pp_hr t formatter =
   formatter
   |> Fmt.fmt "prec "
-  |> Fmt.fmt name
+  |> Fmt.fmt (name t)
 
-let src_fmt {name; prec_set={assoc; stmt; _}} formatter =
+let src_fmt ({prec_set={assoc; stmt; _}; _} as t) formatter =
   let string_of_token token = begin
     Hmc.Source.Slice.to_string (Scan.Token.source token)
   end in
@@ -26,7 +30,7 @@ let src_fmt {name; prec_set={assoc; stmt; _}} formatter =
     | Some Left -> "    left "
     | Some Right -> "    right "
   )
-  |> Fmt.fmt name
+  |> Fmt.fmt (name t)
   |> (fun formatter ->
     match stmt with
     | PrecSet {prec_rels=PrecRelsPrecs {precs=Precs {uident; precs_tl}}; _} -> begin
@@ -48,4 +52,12 @@ let src_fmt {name; prec_set={assoc; stmt; _}} formatter =
   |> Fmt.fmt "\n"
 
 let init ~name ~prec_set =
-  {name; prec_set}
+  let PrecSet.{names; _} = prec_set in
+  let name_index = Array.findi_map ~f:(fun i s ->
+      match String.(name = s) with
+      | true -> Some i
+      | false -> None
+    ) names
+    |> Option.value_hlt
+  in
+  {name_index; prec_set}
diff --git a/bootstrap/bin/hocc/prec.mli b/bootstrap/bin/hocc/prec.mli
index 58edb5ed..12207f51 100644
--- a/bootstrap/bin/hocc/prec.mli
+++ b/bootstrap/bin/hocc/prec.mli
@@ -3,9 +3,10 @@
 open Basis
 open! Basis.Rudiments
 
+module Index = Uns
 type t = {
-  name: string;
-  (** Precedence name. *)
+  name_index: Index.t;
+  (** Index of precedence name within containing precedence set. *)
 
   prec_set: PrecSet.t;
   (** Containing precedence set. *)
@@ -13,6 +14,9 @@ type t = {
 
 include FormattableIntf.SMono with type t := t
 
+val name: t -> string
+(** [name t] returns the precedence name of [t]. *)
+
 val pp_hr: t -> (module Fmt.Formatter) -> (module Fmt.Formatter)
 (** Formatter which outputs precedence in human-readable form. *)
 
@@ -20,4 +24,3 @@ val src_fmt: t -> (module Fmt.Formatter) -> (module Fmt.Formatter)
 (** Formatter which outputs precedence in hocc syntax. *)
 
 val init: name:string -> prec_set:PrecSet.t -> t
-(** Used only by [XXX.init]. *)
diff --git a/bootstrap/bin/hocc/precSet.ml b/bootstrap/bin/hocc/precSet.ml
index 031ba0a3..98f7860c 100644
--- a/bootstrap/bin/hocc/precSet.ml
+++ b/bootstrap/bin/hocc/precSet.ml
@@ -4,7 +4,7 @@ open! Basis.Rudiments
 module Index = Uns
 type t = {
   index: Index.t;
-  names: string list;
+  names: string array;
   assoc: Assoc.t option;
   doms: (Index.t, Index.cmper_witness) Ordset.t;
   stmt: Parse.nonterm_prec_set;
@@ -13,7 +13,7 @@ type t = {
 let pp {index; names; assoc; doms; stmt} formatter =
   formatter
   |> Fmt.fmt "{index=" |> Index.pp index
-  |> Fmt.fmt "; names=" |> List.pp String.pp names
+  |> Fmt.fmt "; names=" |> Array.pp String.pp names
   |> Fmt.fmt "; assoc=" |> (Option.pp Assoc.pp) assoc
   |> Fmt.fmt "; doms=" |> Ordset.pp doms
   |> Fmt.fmt "; stmt=" |> Parse.fmt_prec_set stmt
@@ -22,7 +22,7 @@ let pp {index; names; assoc; doms; stmt} formatter =
 let pp_hr {names; _} formatter =
   formatter
   |> Fmt.fmt "prec "
-  |> Fmt.fmt (String.join ~sep:", " names)
+  |> Fmt.fmt (String.join ~sep:", " (Array.to_list names))
 
 let src_fmt {names; assoc; stmt; _} formatter =
   let string_of_token token = begin
@@ -34,7 +34,7 @@ let src_fmt {names; assoc; stmt; _} formatter =
     | Some Left -> "    left "
     | Some Right -> "    right "
   )
-  |> Fmt.fmt (String.join ~sep:", " names)
+  |> Fmt.fmt (String.join ~sep:", " (Array.to_list names))
   |> (fun formatter ->
     match stmt with
     | PrecSet {prec_rels=PrecRelsPrecs {precs=Precs {uident; precs_tl}}; _} -> begin
diff --git a/bootstrap/bin/hocc/precSet.mli b/bootstrap/bin/hocc/precSet.mli
index fd598931..02d8aee4 100644
--- a/bootstrap/bin/hocc/precSet.mli
+++ b/bootstrap/bin/hocc/precSet.mli
@@ -10,7 +10,7 @@ type t = {
   index: Index.t;
   (** Unique precedence index. *)
 
-  names: string list;
+  names: string array;
   (** Specified precedence names. *)
 
   assoc: Assoc.t option;
@@ -31,6 +31,6 @@ val pp_hr: t -> (module Fmt.Formatter) -> (module Fmt.Formatter)
 val src_fmt: t -> (module Fmt.Formatter) -> (module Fmt.Formatter)
 (** Formatter which outputs precedence set in hocc syntax. *)
 
-val init: index:Index.t -> names:string list -> assoc:(Assoc.t option)
+val init: index:Index.t -> names:string array -> assoc:(Assoc.t option)
   -> doms:(Index.t, Index.cmper_witness) Ordset.t -> stmt:Parse.nonterm_prec_set -> t
 (** Used only by [Precs.init]. *)
diff --git a/bootstrap/bin/hocc/precs.ml b/bootstrap/bin/hocc/precs.ml
index 11b0ea94..a698ba60 100644
--- a/bootstrap/bin/hocc/precs.ml
+++ b/bootstrap/bin/hocc/precs.ml
@@ -13,13 +13,13 @@ let empty = {
 
 let length {prec_sets; _} =
   Ordmap.fold ~init:0L ~f:(fun nprecs (_prec_index, PrecSet.{names; _}) ->
-    nprecs + (List.length names)
+    nprecs + (Array.length names)
   ) prec_sets
 
 let insert ~names ~assoc ~doms ~stmt ({names=names_map; prec_sets} as t) =
   let index = length t in
   let prec_set = PrecSet.init ~index ~names ~assoc ~doms ~stmt in
-  let names_map' = List.fold ~init:names_map ~f:(fun names_map name ->
+  let names_map' = Array.fold ~init:names_map ~f:(fun names_map name ->
     Map.insert_hlt ~k:name ~v:index names_map
   ) names in
   let prec_sets' = Ordmap.insert_hlt ~k:index ~v:prec_set prec_sets in
diff --git a/bootstrap/bin/hocc/precs.mli b/bootstrap/bin/hocc/precs.mli
index 679af903..4d66f6b7 100644
--- a/bootstrap/bin/hocc/precs.mli
+++ b/bootstrap/bin/hocc/precs.mli
@@ -10,7 +10,7 @@ type t
 val empty: t
 (** [empty] returns an empty set of precedences. *)
 
-val insert: names:string list -> assoc:(Assoc.t option)
+val insert: names:string array -> assoc:(Assoc.t option)
   -> doms:(PrecSet.Index.t, PrecSet.Index.cmper_witness) Ordset.t -> stmt:Parse.nonterm_prec_set
   -> t -> t
 (** [insert ~names ~assoc ~doms ~stmt t] creates a [PrecSet.t] with unique index and returns a new
diff --git a/bootstrap/bin/hocc/spec.ml b/bootstrap/bin/hocc/spec.ml
index 661f362b..ce118171 100644
--- a/bootstrap/bin/hocc/spec.ml
+++ b/bootstrap/bin/hocc/spec.ml
@@ -94,7 +94,7 @@ let precs_init io hmh =
         in
         fold_precs_tl_decl io precs names precs_tl
       end
-    | PrecsTlEpsilon -> io, List.rev names
+    | PrecsTlEpsilon -> io, Array.of_list_rev names
   end in
   let fold_precs_decl io precs parse_precs = begin
     match parse_precs with
@@ -129,20 +129,6 @@ let precs_init io hmh =
         in
         let io, names = fold_precs_decl io precs prec_set in
         let precs = Precs.insert ~names ~assoc ~doms ~stmt:parse_prec_set precs in
-
-(*
-        let precs = match Precs.prec_index_of_name name precs with
-          | Some _ -> begin
-              let io =
-                io.err
-                |> Fmt.fmt "hocc: At " |> Hmc.Source.Slice.pp (Scan.Token.source uident)
-                |> Fmt.fmt ": Redefined precedence: " |> Fmt.fmt name |> Fmt.fmt "\n"
-                |> Io.with_err io
-              in
-              Io.fatal io
-            end
-          | None -> Precs.insert ~name ~assoc ~doms ~stmt:parse_prec precs
-*)
         io, precs
       end
   end in
@@ -1054,7 +1040,7 @@ and log_unused io precs symbols prods states =
   let rec mark_prec ~precs_used prec = begin
     match prec with
     | None -> precs_used
-    | Some Prec.{name; _} -> Set.insert name precs_used
+    | Some prec -> Set.insert (Prec.name prec) precs_used
   end
   and mark_symbol ~precs_used ~tokens_used ~nonterms_used
       (Symbol.{index; prec; _} as symbol) = begin
@@ -1129,7 +1115,7 @@ and log_unused io precs symbols prods states =
         |> Fmt.fmt ":\n"
         |> (fun formatter ->
           Precs.fold ~init:formatter ~f:(fun formatter (PrecSet.{names; _} as prec_set) ->
-            List.fold ~init:formatter ~f:(fun formatter name ->
+            Array.fold ~init:formatter ~f:(fun formatter name ->
               match Set.mem name precs_used with
               | true -> formatter
               | false -> begin
@@ -1181,8 +1167,8 @@ and log_unused io precs symbols prods states =
                 |> (fun formatter ->
                   match prec with
                   | None -> formatter
-                  | Some {name; _} ->
-                    formatter |> Fmt.fmt " prec " |> Fmt.fmt name
+                  | Some prec ->
+                    formatter |> Fmt.fmt " " |> Prec.pp_hr prec
                 )
                 |> Fmt.fmt "\n"
               end
@@ -1230,7 +1216,7 @@ and log_unused io precs symbols prods states =
                   |> (fun formatter ->
                     match prec with
                     | None -> formatter
-                    | Some {name; _} -> formatter |> Fmt.fmt " prec " |> Fmt.fmt name
+                    | Some prec -> formatter |> Fmt.fmt " " |> Prec.pp_hr prec
                   )
                   |> Fmt.fmt "\n"
                 end
diff --git a/bootstrap/bin/hocc/symbols.ml b/bootstrap/bin/hocc/symbols.ml
index 72cef9bb..d8ce977d 100644
--- a/bootstrap/bin/hocc/symbols.ml
+++ b/bootstrap/bin/hocc/symbols.ml
@@ -137,7 +137,7 @@ let src_fmt (Symbol.{name; prec; alias; start; prods; _} as symbol) t formatter
       |> (fun formatter ->
         match prec with
         | None -> formatter
-        | Some {name; _} -> formatter |> Fmt.fmt " prec " |> Fmt.fmt name
+        | Some prec -> formatter |> Fmt.fmt " " |> Prec.pp_hr prec
       )
       |> Fmt.fmt "\n"
     end
@@ -151,7 +151,7 @@ let src_fmt (Symbol.{name; prec; alias; start; prods; _} as symbol) t formatter
       |> (fun formatter ->
         match prec with
         | None -> formatter
-        | Some {name; _} -> formatter |> Fmt.fmt " prec " |> Fmt.fmt name
+        | Some prec -> formatter |> Fmt.fmt " " |> Prec.pp_hr prec
       )
       |> Fmt.fmt " ::="
       |> Fmt.fmt (match Ordset.length prods with
@@ -187,7 +187,7 @@ let src_fmt (Symbol.{name; prec; alias; start; prods; _} as symbol) t formatter
             | None, None
             | Some _, Some _ (* Re-normalize; prec was propagated from symbol. *)
               -> formatter
-            | None, Some {name; _} -> formatter |> Fmt.fmt " prec " |> Fmt.fmt name
+            | None, Some prec -> formatter |> Fmt.fmt " " |> Prec.pp_hr prec
             | Some _, None -> not_reached ()
           )
           |> Fmt.fmt "\n"