haskell: Phase 13 — Ord default verification (myMax/myMin) (+5 tests, 10/10)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/haskell/tests/class-defaults.sx

@@ -35,4 +35,33 @@
       "class Hi a where\n  greet :: a -> String\n  greet x = \"default\"\ninstance Hi Bool where\nmain = greet True"))
   "default")
 
+(define
+  hk-myord-source
+  "class MyOrd a where\n  myCmp :: a -> a -> Bool\n  myMax :: a -> a -> a\n  myMin :: a -> a -> a\n  myMax a b = if myCmp a b then a else b\n  myMin a b = if myCmp a b then b else a\ninstance MyOrd Int where\n  myCmp x y = x >= y\n")
+
+(hk-test
+  "Ord default: myMax 3 5 = 5"
+  (hk-deep-force (hk-run (str hk-myord-source "main = myMax 3 5\n")))
+  5)
+
+(hk-test
+  "Ord default: myMax 8 2 = 8"
+  (hk-deep-force (hk-run (str hk-myord-source "main = myMax 8 2\n")))
+  8)
+
+(hk-test
+  "Ord default: myMin 3 5 = 3"
+  (hk-deep-force (hk-run (str hk-myord-source "main = myMin 3 5\n")))
+  3)
+
+(hk-test
+  "Ord default: myMin 8 2 = 2"
+  (hk-deep-force (hk-run (str hk-myord-source "main = myMin 8 2\n")))
+  2)
+
+(hk-test
+  "Ord default: myMax of equals returns first"
+  (hk-deep-force (hk-run (str hk-myord-source "main = myMax 4 4\n")))
+  4)
+
 {:fails hk-test-fails :pass hk-test-pass :fail hk-test-fail}

plans/haskell-completeness.md

@@ -232,7 +232,7 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
   explicit `/=` in every Eq instance. _Verified using a `MyEq`/`myNeq` class
   + instance test (operator-style `(/=)` is a parser concern; the default
   mechanism itself is verified)._
-- [ ] `Ord` defaults: `max a b = if a >= b then a else b`, `min a b = if a <=
+- [x] `Ord` defaults: `max a b = if a >= b then a else b`, `min a b = if a <=
   b then a else b`. Verify.
 - [ ] `Num` defaults: `negate x = 0 - x`, `abs x = if x < 0 then negate x else x`,
   `signum x = if x > 0 then 1 else if x < 0 then -1 else 0`. Verify.
@@ -309,6 +309,11 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
 
 _Newest first._
 
+**2026-05-07** — Phase 13 Ord-style default verification:
+- Added 5 tests to `class-defaults.sx` for myMax/myMin defined as defaults
+  in terms of `myCmp` (≥). Verified myMax/myMin on (3,5), (8,2), (4,4).
+  Suite is now 10/10.
+
 **2026-05-07** — Phase 13 Eq-style default verification:
 - New `tests/class-defaults.sx` (5 tests) seeds the class-defaults test file.
   Covers a 2-arg default method (`myNeq x y = not (myEq x y)`) where the