apl: primes sieve (2=+⌿0=A∘.|A)/A←⍳N + apl-compress (+11 tests, 280/280)

lib/apl/conformance.sh

@@ -13,7 +13,7 @@ if [ ! -x "$SX_SERVER" ]; then
   exit 1
 fi
 
-SUITES=(structural operators dfn tradfn valence)
+SUITES=(structural operators dfn tradfn valence programs)
 
 OUT_JSON="lib/apl/scoreboard.json"
 OUT_MD="lib/apl/scoreboard.md"

lib/apl/runtime.sx

@@ -796,6 +796,34 @@
         ((result (filter (fn (x) (not (index-of b-ravel x))) a-ravel)))
         (make-array (list (len result)) result)))))
 
+(define
+  apl-compress
+  (fn
+    (mask arr)
+    (let
+      ((mask-ravel (get mask :ravel)) (arr-ravel (get arr :ravel)))
+      (let
+        ((kept (filter (fn (i) (not (= 0 (nth mask-ravel i)))) (range 0 (len arr-ravel)))))
+        (let
+          ((picked (map (fn (i) (nth arr-ravel i)) kept)))
+          (make-array (list (len picked)) picked))))))
+
+(define
+  apl-primes
+  (fn
+    (n)
+    (let
+      ((a (apl-iota (apl-scalar n))))
+      (let
+        ((mod-table (apl-outer apl-mod a a)))
+        (let
+          ((zero-mask (apl-eq (apl-scalar 0) mod-table)))
+          (let
+            ((divisor-counts (apl-reduce-first apl-add zero-mask)))
+            (let
+              ((prime-mask (apl-eq (apl-scalar 2) divisor-counts)))
+              (apl-compress prime-mask a))))))))
+
 (define
   apl-reduce
   (fn

lib/apl/scoreboard.json

@@ -4,9 +4,10 @@
     "operators": {"pass": 117, "fail": 0},
     "dfn": {"pass": 24, "fail": 0},
     "tradfn": {"pass": 20, "fail": 0},
-    "valence": {"pass": 14, "fail": 0}
+    "valence": {"pass": 14, "fail": 0},
+    "programs": {"pass": 11, "fail": 0}
   },
-  "total_pass": 269,
+  "total_pass": 280,
   "total_fail": 0,
-  "total": 269
+  "total": 280
 }

lib/apl/scoreboard.md

@@ -9,7 +9,8 @@ _Generated by `lib/apl/conformance.sh`_
 | dfn | 24 | 0 | 24 |
 | tradfn | 20 | 0 | 20 |
 | valence | 14 | 0 | 14 |
-| **Total** | **269** | **0** | **269** |
+| programs | 11 | 0 | 11 |
+| **Total** | **280** | **0** | **280** |
 
 ## Notes
 

lib/apl/test.sh

@@ -31,6 +31,7 @@ cat > "$TMPFILE" << 'EPOCHS'
 (load "lib/apl/tests/dfn.sx")
 (load "lib/apl/tests/tradfn.sx")
 (load "lib/apl/tests/valence.sx")
+(load "lib/apl/tests/programs.sx")
 (epoch 4)
 (eval "(list apl-test-pass apl-test-fail)")
 EPOCHS

lib/apl/tests/programs.sx

@@ -0,0 +1,58 @@
+; Tests for classic APL programs (lib/apl/tests/programs/*.apl).
+; Programs are showcase APL source; runtime impl is in lib/apl/runtime.sx.
+
+(define mkrv (fn (arr) (get arr :ravel)))
+(define mksh (fn (arr) (get arr :shape)))
+
+; ===== primes (Sieve of Eratosthenes) =====
+
+(apl-test "primes 1 → empty" (mkrv (apl-primes 1)) (list))
+
+(apl-test "primes 2 → just 2" (mkrv (apl-primes 2)) (list 2))
+
+(apl-test "primes 10 → 2 3 5 7" (mkrv (apl-primes 10)) (list 2 3 5 7))
+
+(apl-test
+  "primes 20 → 2 3 5 7 11 13 17 19"
+  (mkrv (apl-primes 20))
+  (list 2 3 5 7 11 13 17 19))
+
+(apl-test
+  "primes 30"
+  (mkrv (apl-primes 30))
+  (list 2 3 5 7 11 13 17 19 23 29))
+
+(apl-test
+  "primes 50"
+  (mkrv (apl-primes 50))
+  (list 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47))
+
+(apl-test "primes 7 length" (first (mksh (apl-primes 7))) 4)
+
+(apl-test "primes 100 has 25 primes" (first (mksh (apl-primes 100))) 25)
+
+; ===== compress helper sanity =====
+
+(apl-test
+  "compress 1 0 1 0 1 / 10 20 30 40 50"
+  (mkrv
+    (apl-compress
+      (make-array (list 5) (list 1 0 1 0 1))
+      (make-array (list 5) (list 10 20 30 40 50))))
+  (list 10 30 50))
+
+(apl-test
+  "compress all-zero mask → empty"
+  (mkrv
+    (apl-compress
+      (make-array (list 3) (list 0 0 0))
+      (make-array (list 3) (list 1 2 3))))
+  (list))
+
+(apl-test
+  "compress all-one mask → full vector"
+  (mkrv
+    (apl-compress
+      (make-array (list 3) (list 1 1 1))
+      (make-array (list 3) (list 1 2 3))))
+  (list 1 2 3))

lib/apl/tests/programs/primes.apl

@@ -0,0 +1,16 @@
+⍝ Sieve of Eratosthenes — the classic APL one-liner
+⍝   primes ← (2=+⌿0=A∘.|A)/A←⍳N
+⍝
+⍝ Read right-to-left:
+⍝   A ← ⍳N        : A is 1..N
+⍝   A∘.|A         : outer-product residue table — M[i,j] = A[j] mod A[i]
+⍝   0=...         : boolean — true where A[i] divides A[j]
+⍝   +⌿...         : column sums — count of divisors per A[j]
+⍝   2=...         : true for numbers with exactly 2 divisors (1 and self) → primes
+⍝   .../A         : compress — select A[j] where mask[j] is true
+⍝
+⍝ Examples:
+⍝   primes 10  →  2 3 5 7
+⍝   primes 30  →  2 3 5 7 11 13 17 19 23 29
+
+primes ← {(2=+⌿0=⍵∘.|⍵)/⍵←⍳⍵}