erlang: ring.erl + call/cc suspension rewrite (+4 ring tests)

lib/erlang/tests/programs/ring.sx

@@ -0,0 +1,132 @@
+;; Ring program — N processes in a ring, token passes M times.
+;;
+;; Each process waits for {setup, Next} so main can tie the knot
+;; (can't reference a pid before spawning it). Once wired, main
+;; injects the first token; each process forwards decrementing K
+;; until it hits 0, at which point it signals `done` to main.
+
+(define er-ring-test-count 0)
+(define er-ring-test-pass 0)
+(define er-ring-test-fails (list))
+
+(define
+  er-ring-test
+  (fn
+    (name actual expected)
+    (set! er-ring-test-count (+ er-ring-test-count 1))
+    (if
+      (= actual expected)
+      (set! er-ring-test-pass (+ er-ring-test-pass 1))
+      (append! er-ring-test-fails {:actual actual :expected expected :name name}))))
+
+(define ring-ev erlang-eval-ast)
+
+(define
+  er-ring-program-3-6
+  "Me = self(),
+   Spawner = fun () ->
+     receive {setup, Next} ->
+       Loop = fun () ->
+         receive
+           {token, 0, Parent} -> Parent ! done;
+           {token, K, Parent} -> Next ! {token, K-1, Parent}, Loop()
+         end
+       end,
+       Loop()
+     end
+   end,
+   P1 = spawn(Spawner),
+   P2 = spawn(Spawner),
+   P3 = spawn(Spawner),
+   P1 ! {setup, P2},
+   P2 ! {setup, P3},
+   P3 ! {setup, P1},
+   P1 ! {token, 5, Me},
+   receive done -> finished end")
+
+(er-ring-test
+  "ring N=3 M=6"
+  (get (ring-ev er-ring-program-3-6) :name)
+  "finished")
+
+;; Two-node ring — token bounces twice between P1 and P2.
+(er-ring-test
+  "ring N=2 M=4"
+  (get (ring-ev
+    "Me = self(),
+     Spawner = fun () ->
+       receive {setup, Next} ->
+         Loop = fun () ->
+           receive
+             {token, 0, Parent} -> Parent ! done;
+             {token, K, Parent} -> Next ! {token, K-1, Parent}, Loop()
+           end
+         end,
+         Loop()
+       end
+     end,
+     P1 = spawn(Spawner),
+     P2 = spawn(Spawner),
+     P1 ! {setup, P2},
+     P2 ! {setup, P1},
+     P1 ! {token, 3, Me},
+     receive done -> done end") :name)
+  "done")
+
+;; Single-node "ring" — P sends to itself M times.
+(er-ring-test
+  "ring N=1 M=5"
+  (get (ring-ev
+    "Me = self(),
+     Spawner = fun () ->
+       receive {setup, Next} ->
+         Loop = fun () ->
+           receive
+             {token, 0, Parent} -> Parent ! finished_loop;
+             {token, K, Parent} -> Next ! {token, K-1, Parent}, Loop()
+           end
+         end,
+         Loop()
+       end
+     end,
+     P = spawn(Spawner),
+     P ! {setup, P},
+     P ! {token, 4, Me},
+     receive finished_loop -> ok end") :name)
+  "ok")
+
+;; Confirm the token really went around — count hops via io-buffer.
+(er-ring-test
+  "ring N=3 M=9 hop count"
+  (do
+    (er-io-flush!)
+    (ring-ev
+      "Me = self(),
+       Spawner = fun () ->
+         receive {setup, Next} ->
+           Loop = fun () ->
+             receive
+               {token, 0, Parent} -> Parent ! done;
+               {token, K, Parent} ->
+                 io:format(\"~p \", [K]),
+                 Next ! {token, K-1, Parent},
+                 Loop()
+             end
+           end,
+           Loop()
+         end
+       end,
+       P1 = spawn(Spawner),
+       P2 = spawn(Spawner),
+       P3 = spawn(Spawner),
+       P1 ! {setup, P2},
+       P2 ! {setup, P3},
+       P3 ! {setup, P1},
+       P1 ! {token, 8, Me},
+       receive done -> done end")
+    (er-io-buffer-content))
+  "8 7 6 5 4 3 2 1 ")
+
+(define
+  er-ring-test-summary
+  (str "ring " er-ring-test-pass "/" er-ring-test-count))