apl: ∪ unique / ∪ union / ∩ intersection (+12)

- apl-unique: dedup keeping first-occurrence order
- apl-union: dedup'd A then B-elements-not-in-A
- apl-intersect: A elements that are in B, preserves left order
- ∪ wired both monadic and dyadic; ∩ wired dyadic
- pipeline 121/121

lib/apl/tests/pipeline.sx

@@ -497,3 +497,50 @@
     "⍸ interval-index: y above all → len breaks"
     (mkrv (apl-run "10 20 30 ⍸ 100"))
     (list 3)))
+
+(begin
+  (apl-test
+    "∪ unique: dedup keeps first-occurrence order"
+    (mkrv (apl-run "∪ 1 2 1 3 2 1 4"))
+    (list 1 2 3 4))
+  (apl-test
+    "∪ unique: already-unique unchanged"
+    (mkrv (apl-run "∪ 5 4 3 2 1"))
+    (list 5 4 3 2 1))
+  (apl-test "∪ unique: scalar" (mkrv (apl-run "∪ 7")) (list 7))
+  (apl-test
+    "∪ unique: string mississippi → misp"
+    (mkrv (apl-run "∪ 'mississippi'"))
+    (list "m" "i" "s" "p"))
+  (apl-test
+    "∪ union: 1 2 3 ∪ 3 4 5 → 1 2 3 4 5"
+    (mkrv (apl-run "1 2 3 ∪ 3 4 5"))
+    (list 1 2 3 4 5))
+  (apl-test
+    "∪ union: dedups left side too"
+    (mkrv (apl-run "1 2 1 ∪ 1 3 2"))
+    (list 1 2 3))
+  (apl-test
+    "∪ union: disjoint → catenated"
+    (mkrv (apl-run "1 2 ∪ 3 4"))
+    (list 1 2 3 4))
+  (apl-test
+    "∩ intersection: 1 2 3 4 ∩ 2 4 6 → 2 4"
+    (mkrv (apl-run "1 2 3 4 ∩ 2 4 6"))
+    (list 2 4))
+  (apl-test
+    "∩ intersection: disjoint → empty"
+    (mkrv (apl-run "1 2 3 ∩ 4 5 6"))
+    (list))
+  (apl-test
+    "∩ intersection: preserves left order"
+    (mkrv (apl-run "(⍳5) ∩ 5 3 1"))
+    (list 1 3 5))
+  (apl-test
+    "∩ intersection: identical"
+    (mkrv (apl-run "1 2 3 ∩ 1 2 3"))
+    (list 1 2 3))
+  (apl-test
+    "∪/∩ identity: A ∪ A = ∪A"
+    (mkrv (apl-run "1 2 1 ∪ 1 2 1"))
+    (list 1 2)))