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

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

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+⍝ 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=⍵∘.|⍵)/⍵←⍳⍵}