haskell: lazy sieve of Eratosthenes (+mod/div/rem/quot, +2 tests, 390/390)

lib/haskell/tests/program-sieve.sx

@@ -0,0 +1,48 @@
+;; sieve.hs — lazy sieve of Eratosthenes.
+;;
+;; The canonical artefact lives at lib/haskell/tests/programs/sieve.hs.
+;; Mirrored here as an SX string because the default eval env has no
+;; read-file. Uses filter + backtick `mod` + lazy [2..] — all of which
+;; are now wired in via Phase 3 + the mod/div additions to hk-binop.
+
+(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-prog-val
+  (fn
+    (src name)
+    (hk-deep-force (get (hk-eval-program (hk-core src)) name))))
+
+(define
+  hk-sieve-source
+  "sieve (p:xs) = p : sieve (filter (\\x -> x `mod` p /= 0) xs)
+sieve [] = []
+primes = sieve [2..]
+result = take 10 primes
+")
+
+(hk-test
+  "sieve.hs — first 10 primes"
+  (hk-as-list (hk-prog-val hk-sieve-source "result"))
+  (list 2 3 5 7 11 13 17 19 23 29))
+
+(hk-test
+  "sieve.hs — 20th prime is 71"
+  (nth
+    (hk-as-list
+      (hk-prog-val
+        (str
+          hk-sieve-source
+          "result20 = take 20 primes\n")
+        "result20"))
+    19)
+  71)
+
+{:fails hk-test-fails :pass hk-test-pass :fail hk-test-fail}