ocaml: phase 2 evaluator slice (+42 tests, 165 total)

ocaml-eval walks the AST and yields SX values. ocaml-run / ocaml-run-program
wrap parse + eval. Coverage: atoms, vars, app (curried), 22 binary ops,
prefix - and not, if/seq/tuple/list, fun (auto-curried via host SX
lambdas), let, let-rec (mutable-cell knot for recursive functions).
Initial env: not/succ/pred/abs/max/min/fst/snd/ignore. Tests: arithmetic,
comparison, string concat, closures, fact 5 / fib 10 / sum 100,
top-level decls, |> pipe.

plans/ocaml-on-sx.md

@@ -144,13 +144,15 @@ SX CEK evaluator (both JS and OCaml hosts)
 
 ### Phase 2 — Core evaluator (untyped)
 
-- [ ] `ocaml-eval` entry: walks OCaml AST, produces SX values.
-- [ ] `let`/`let rec`/`let ... in` (mutually recursive with `and`).
-- [ ] Lambda + application (curried by default — auto-curry multi-param defs).
-- [ ] `fun`/`function` (single-arg lambda with immediate match on arg).
-- [ ] `if`/`then`/`else`, `begin`/`end`, sequence `;`.
-- [ ] Arithmetic, comparison, boolean ops, string `^`, `mod`.
-- [ ] Unit `()` value; `ignore`.
+- [x] `ocaml-eval` entry: walks OCaml AST, produces SX values.
+- [~] `let`/`let rec`/`let ... in` (single-binding done; mutually recursive
+      `and` deferred).
+- [x] Lambda + application (curried by default — auto-curry multi-param defs).
+- [ ] `fun`/`function` (single-arg lambda with immediate match on arg). _(`fun`
+      done; `function` blocked on parser support.)_
+- [x] `if`/`then`/`else`, `begin`/`end`, sequence `;`.
+- [x] Arithmetic, comparison, boolean ops, string `^`, `mod`.
+- [x] Unit `()` value; `ignore`.
 - [ ] References: `ref`, `!`, `:=`.
 - [ ] Mutable record fields.
 - [ ] `for i = lo to hi do ... done` loop; `while cond do ... done`.
@@ -315,6 +317,16 @@ the "mother tongue" closure: OCaml → SX → OCaml. This means:
 
 _Newest first._
 
+- 2026-05-08 Phase 2 — `lib/ocaml/eval.sx`: ocaml-eval + ocaml-run +
+  ocaml-run-program. Coverage: atoms, var lookup, :app (curried),
+  :op (arithmetic/comparison/boolean/^/mod/::/|>), :neg, :not, :if,
+  :seq, :tuple, :list, :fun (auto-curried host-SX closures), :let,
+  :let-rec (recursive knot via one-element-list mutable cell). Initial
+  env exposes `not`/`succ`/`pred`/`abs`/`max`/`min`/`fst`/`snd`/`ignore`
+  as host-SX functions. Tests: literals, arithmetic, comparison, boolean,
+  string concat, conditionals, lambda + closures + recursion (fact 5,
+  fib 10, sum 100), sequences, top-level program decls, |> pipe. 165/165
+  passing (+42).
 - 2026-05-07 Phase 1 — sequence operator `;`. Lowest-precedence binary;
   `e1; e2; e3` → `(:seq e1 e2 e3)`. Two-phase grammar: `parse-expr-no-seq`
   is the prior expression entry point; new `parse-expr` wraps it with