ocaml: phase 6 List.sort_uniq + List.find_map (+2 tests, 503 total)

sort_uniq:
  Sort with the user comparator, then walk the sorted list dropping
  any element equal to its predecessor. Output is sorted and unique.

  List.sort_uniq compare [3;1;2;1;3;2;4]  =  [1;2;3;4]

find_map:
  Walk until the user fn returns Some v; return that. If all None,
  return None.

  List.find_map (fun x -> if x > 5 then Some (x * 2) else None)
                [1;2;3;6;7]
  = Some 12

Both defined in OCaml syntax in runtime.sx — no host primitive
needed since they're pure list traversals over existing operations.

lib/ocaml/runtime.sx

@@ -158,6 +158,26 @@
 
      let stable_sort = sort
 
+     let rec sort_uniq cmp xs =
+       let sorted = sort cmp xs in
+       let rec dedup ys =
+         match ys with
+         | [] -> []
+         | [x] -> [x]
+         | a :: b :: rest ->
+           if cmp a b = 0 then dedup (b :: rest)
+           else a :: dedup (b :: rest)
+       in
+       dedup sorted
+
+     let rec find_map f xs =
+       match xs with
+       | [] -> None
+       | h :: t ->
+         match f h with
+         | Some v -> Some v
+         | None -> find_map f t
+
      let rec combine xs ys =
        match xs with
        | [] -> (match ys with

lib/ocaml/test.sh

@@ -1248,6 +1248,12 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 4982)
 (eval "(ocaml-run \"String.of_seq (List.rev (String.to_seq \\\"hello\\\"))\")")
 
+;; ── List.sort_uniq / List.find_map ───────────────────────────
+(epoch 4990)
+(eval "(ocaml-run \"List.sort_uniq compare [3;1;2;1;3;2;4]\")")
+(epoch 4991)
+(eval "(ocaml-run \"List.find_map (fun x -> if x > 5 then Some (x * 2) else None) [1;2;3;6;7]\")")
+
 EPOCHS
 
 OUTPUT=$(timeout 360 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -1981,6 +1987,10 @@ check 4980 "String.iter sum codes abc"    '294'
 check 4981 "String.fold_left sum hi"      '209'
 check 4982 "String.of_seq (rev to_seq)"   '"olleh"'
 
+# ── List.sort_uniq / List.find_map ──────────────────────────────
+check 4990 "sort_uniq dedupes & sorts"    '(1 2 3 4)'
+check 4991 "find_map first >5 doubled"    '("Some" 12)'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "ok $PASS/$TOTAL OCaml-on-SX tests passed"

plans/ocaml-on-sx.md

@@ -407,6 +407,11 @@ _Newest first._
   binary search tree (`type 'a tree = Leaf | Node of 'a * 'a tree *
   'a tree`) with insert + in-order traversal. Tests parametric ADT,
   recursive match, List.append, List.fold_left.
+- 2026-05-09 Phase 6 — List.sort_uniq / List.find_map (+2 tests, 503
+  total). sort_uniq sorts then dedups consecutive equals. find_map
+  walks until the user fn returns `Some v` and returns it (or `None`
+  on empty/all-None). Closes two of the most-asked-for list ops; both
+  defined in OCaml syntax in runtime.sx.
 - 2026-05-09 Phase 6 — String.iter / iteri / fold_left / fold_right /
   to_seq / of_seq (+3 tests, 501 total). All implemented in OCaml
   syntax inside the runtime stdlib; iter / iteri walk via index +