Adding some erlang stuff.

pe/ring.erl

@@ -5,3 +5,47 @@
 %% Write a similar program in some other programming language you are
 %% familiar with. Compare the results. Write a blog, and publish the
 %% results on the internet!
+-module(ring).
+-compile(export_all). % TODO: remove this
+-record(message, {client=undefined, ttl=0, hops=0}).
+
+%% What does a loop need to know? Who to forward to next. 
+%%
+%% How does the last node know who to forward to? We need to pass the
+%% parent in somehow.
+%% 
+loop(Next) ->
+    receive
+	#message{client=Client, ttl=TTL, hops=Hops} ->
+	    if TTL > 0 ->
+		    Next ! #message{client=Client, ttl=TTL-1, hops=Hops};
+	       true ->
+		    Client ! #message{client=Client, ttl=TTL, hops=Hops}
+	    end
+    end.
+
+
+%% gen_process ->
+%%   1. is N > 0?
+%%      1. Spawn process, use self() as next.
+%%         This generates processes in the reverse order, e.g.
+%%         this process is the last process in the chain.
+
+gen_process(N) when is_number(N) ->
+    Root = self(),
+    Child = gen_process(Root, Root, N-1),
+    loop(Child).
+    
+gen_process(Root, _Parent, 0) ->
+    loop(Root);
+
+gen_process(Root, Parent, Count) when Count > 0 ->
+    Child = gen_process(Root, Parent, Count-1),
+    loop(Child).
+
+ring(N) ->
+    Root = spawn(fun () -> gen_process(N) end),
+    Root ! #message{client=self(), ttl=N, hops=0},
+    receive X ->
+	    X
+    end.

pe/ring.go

@@ -1,6 +1,53 @@
 package main
 
+import (
+	"fmt"
+	"time"
+)
+
 type Message struct {
-	RCount int // how many times around the ring have we been
-	FCount int // how many times has the message been forwarded
+	TTL    int
+	Parent chan Message
+}
+
+func process(from, next chan Message, id int) {
+	fmt.Printf("PID %d: from=%p, next=%p\n", id, from, next)
+	for {
+		message, ok := <-from
+		if !ok {
+			return
+		}
+
+		fmt.Printf("process %d: message: %+v\n", message)
+		message.TTL--
+		if message.TTL == 0 {
+			message.Parent <- message
+		}
+
+		next <- message
+	}
+}
+
+func genProcess(count int) chan Message {
+	fmt.Printf("spawn: %p, count=%d\n", from, count)
+	next := make(chan Message, 0)
+	count--
+	go process(from, next, count)
+	if count == 0 {
+		return from
+	}
+
+	return genProcess(next, count)
+}
+
+func main() {
+	fmt.Println("startup")
+	entrypoint := make(chan Message, 0)
+	ring := genProcess(entrypoint, 3)
+	fmt.Printf("%p\t%p\n", ring, entrypoint)
+	time.Sleep(1)
+	rcv := make(chan Message, 0)
+	message := Message{3, rcv}
+	message = <-rcv
+	fmt.Println(message)
 }