“Kragen: Transactional backing store is a completely different issue. SQL databases have been transactional since forever (to first approximation)….The transactional store is generally only accessed through some discreet interface (SQL or some special library API), making accessing the transactional store in a non-transactional way much more difficult.”

That’s why I mentioned ZODB, GemStone, and ObjectStore, for which the transactional store is not accessed through a separate interface; persistent objects act more or less exactly like ordinary non-persistent objects. (I think this is the case for CICS too, which is why I mentioned it, but I don’t have deep enough knowledge of CICS.) I can’t tell if you didn’t read my comment very carefully or if you just didn’t know about these systems.

public class Stack{

private Node head;

public void push(E item) {
if (item == null) throw new NullPointerException();
head = new Node(item, head);
}

public E peek() {
if (head == null)
return null;

return removeTopItem();
}

public E pop() {
if (head == null)
retry();

return removeTopItem();
}

private E removeTopItem() {
Node oldHead = head;
head = head.parent;
return oldHead.value;
}

public int size() {
return head == null ? 0 : head.size();
}

public boolean isEmpty() {
return size() == 0;
}

public static class Node {
final E value;
final Node parent;
final int size;

Node(E value, Node prev) {
this.value = value;
this.parent = prev;
this.size = parent == null ? 1 : prev.size+1;
}

int size() {
return size;
}
}
}

As you can see, the language doesn’t need to suck if you use an STM.

You can check http://code.google.com/p/multiverse/ if the layout of the example is f*cked up.

Write your launch-missiles using io!:

(defn launch-missiles
“Launch attack on remote targets with everything we have.”
[]
(io!
(doseq [missile (all-silos)]
(fire missile))))

Now whenever you try to launch the missiles inside a transaction,
Clojure will tell you. Safety switch: “ON”.