haskell: 13 new program suites + scoreboard 156/156 (775 tests)

collatz, palindrome, maybe, fizzbuzz, anagram, roman, binary, either,
primes, zipwith, matrix, wordcount, powers — all 18/18 programs green.
conformance.sh PROGRAMS array updated; scoreboard.md regenerated.

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

lib/haskell/tests/program-maybe.sx

@@ -0,0 +1,83 @@
+;; maybe.hs — safe operations returning Maybe values.
+
+(define
+  hk-prog-val
+  (fn
+    (src name)
+    (hk-deep-force (get (hk-eval-program (hk-core src)) name))))
+
+(define
+  hk-as-list
+  (fn
+    (xs)
+    (cond
+      ((and (list? xs) (= (first xs) "[]")) (list))
+      ((and (list? xs) (= (first xs) ":"))
+        (cons (nth xs 1) (hk-as-list (nth xs 2))))
+      (:else xs))))
+
+(define
+  hk-maybe-src
+  "safeDiv _ 0 = Nothing\nsafeDiv x y = Just (x `div` y)\n\nsafeHead [] = Nothing\nsafeHead (x:_) = Just x\n\nfromMaybeZero Nothing = 0\nfromMaybeZero (Just x) = x\n\nmapMaybe _ Nothing = Nothing\nmapMaybe f (Just x) = Just (f x)\n\ndouble x = x * 2\n")
+
+(hk-test
+  "safeDiv 10 2 = Just 5"
+  (hk-prog-val (str hk-maybe-src "r = safeDiv 10 2\n") "r")
+  (list "Just" 5))
+
+(hk-test
+  "safeDiv 7 0 = Nothing"
+  (hk-prog-val (str hk-maybe-src "r = safeDiv 7 0\n") "r")
+  (list "Nothing"))
+
+(hk-test
+  "safeHead [1,2,3] = Just 1"
+  (hk-prog-val (str hk-maybe-src "r = safeHead [1,2,3]\n") "r")
+  (list "Just" 1))
+
+(hk-test
+  "safeHead [] = Nothing"
+  (hk-prog-val (str hk-maybe-src "r = safeHead []\n") "r")
+  (list "Nothing"))
+
+(hk-test
+  "fromMaybeZero Nothing = 0"
+  (hk-prog-val (str hk-maybe-src "r = fromMaybeZero Nothing\n") "r")
+  0)
+
+(hk-test
+  "fromMaybeZero (Just 42) = 42"
+  (hk-prog-val (str hk-maybe-src "r = fromMaybeZero (Just 42)\n") "r")
+  42)
+
+(hk-test
+  "mapMaybe double Nothing = Nothing"
+  (hk-prog-val (str hk-maybe-src "r = mapMaybe double Nothing\n") "r")
+  (list "Nothing"))
+
+(hk-test
+  "mapMaybe double (Just 5) = Just 10"
+  (hk-prog-val (str hk-maybe-src "r = mapMaybe double (Just 5)\n") "r")
+  (list "Just" 10))
+
+(hk-test
+  "chain: fromMaybeZero (safeDiv 10 2) = 5"
+  (hk-prog-val (str hk-maybe-src "r = fromMaybeZero (safeDiv 10 2)\n") "r")
+  5)
+
+(hk-test
+  "chain: fromMaybeZero (safeDiv 10 0) = 0"
+  (hk-prog-val (str hk-maybe-src "r = fromMaybeZero (safeDiv 10 0)\n") "r")
+  0)
+
+(hk-test
+  "safeDiv 100 5 = Just 20"
+  (hk-prog-val (str hk-maybe-src "r = safeDiv 100 5\n") "r")
+  (list "Just" 20))
+
+(hk-test
+  "mapMaybe double (safeDiv 6 2) = Just 6"
+  (hk-prog-val (str hk-maybe-src "r = mapMaybe double (safeDiv 6 2)\n") "r")
+  (list "Just" 6))
+
+{:fails hk-test-fails :pass hk-test-pass :fail hk-test-fail}