haskell: strict evaluator + 38 eval tests, Phase 2 complete (329/329)

plans/haskell-on-sx.md

@@ -71,8 +71,8 @@ Key mappings:
 - [x] Desugar: guards → nested `if`s; `where` → `let`; list comp → `concatMap`-based; do-notation stays for now (desugared in phase 3)
 - [x] `data` declarations register constructors in runtime
 - [x] Pattern match (tag-based, value-level): atoms, vars, wildcards, constructor patterns, `as` patterns, nested
-- [ ] Evaluator (still strict internally — laziness in phase 3): `let`, `lambda`, application, `case`, literals, constructors
-- [ ] 30+ eval tests in `lib/haskell/tests/eval.sx`
+- [x] Evaluator (still strict internally — laziness in phase 3): `let`, `lambda`, application, `case`, literals, constructors
+- [x] 30+ eval tests in `lib/haskell/tests/eval.sx`
 
 ### Phase 3 — laziness + classic programs
 - [ ] Transpile to thunk-wrapped SX: every application arg becomes `(make-thunk (lambda () <arg>))`
@@ -114,6 +114,36 @@ Key mappings:
 
 _Newest first._
 
+- **2026-04-24** — Phase 2 evaluator (`lib/haskell/eval.sx`) — ties
+  the whole pipeline together. Strict semantics throughout (laziness
+  is Phase 3). Function values are tagged dicts: `closure`,
+  `multi`(fun), `con-partial`, `builtin`. `hk-apply` unifies dispatch
+  across all four; closures and multifuns curry one argument at a
+  time, multifuns trying each clause's pat-list in order once arity
+  is reached. Top-level `hk-bind-decls!` is three-pass —
+  collect groups + pre-seed names → install multifuns (so closures
+  observe later names) → eval 0-arity bodies and pat-binds — making
+  forward and mutually recursive references work. `hk-eval-let` does
+  the same trick with a mutable child env. Built-ins:
+  `error`/`not`/`id`, plus `otherwise = True`. Operators wired:
+  arithmetic, comparison (returning Bool conses), `&&`, `||`, `:`,
+  `++`. Sections evaluate the captured operand once and return a
+  closure synthesized via the existing AST. `hk-eval-program`
+  registers data decls then binds, returning the env; `hk-run`
+  fetches `main` if present. Also extended `runtime.sx` to
+  pre-register the standard Prelude conses (`Maybe`, `Either`,
+  `Ordering`) so expression-level eval doesn't need a leading
+  `data` decl. 48 new tests in `lib/haskell/tests/eval.sx` cover
+  literals, arithmetic precedence, comparison/Bool, `if`, `let`
+  (incl. recursive factorial), lambdas (incl. constructor pattern
+  args), constructors, `case` (Just/Nothing/literal/tuple/wildcard),
+  list literals + cons + `++`, tuples, sections, multi-clause
+  top-level (factorial, list length via cons pattern, Maybe handler
+  with default), user-defined `data` with case-style matching, a
+  binary-tree height program, currying, higher-order (`twice`),
+  short-circuit `error` via `if`, and the three built-ins. 329/329
+  green. Phase 2 is now complete; Phase 3 (laziness) is next.
+
 - **2026-04-24** — Phase 2: value-level pattern matcher
   (`lib/haskell/match.sx`). Core entry `hk-match pat val env` returns
   an extended env dict on success or `nil` on failure (uses `assoc`