Thanks Ken, I found this too when I saw Tassilo's problem on irc
(didn't notice it was on ML as well). I was going submit a patch for
this, but if you've already done so let me know and I won't.
On Mar 14, 12:37 pm, Ken Wesson <kwess...@gmail.com> wrote:
> On Mon, Mar 14, 2011 at 4:13 PM, Tassilo Horn <tass...@member.fsf.org> wrote:
> > Hi all,
>
> > I've implemented IEditableCollection support for ninjudd's
> > PersistentOrderedSet. But when using that, my application delivered
> > wrong results. See <87hbb6c4qf....@member.fsf.org> and follow-ups.
>
> > I was able to track it down to the strangeness in the subject:
>
> > (.contains (transient (hash-set)) foo)
>
> > returns true for any object foo, that is, the empty transient hash-set
> > contains everything.
>
> > The above clojure code is equivalent to this java code, which I used in
> > the PersistentOrderedSet extension:
>
> > ((ITransientSet) PersistentHashSet.EMPTY.asTransient()).contains(o)
>
> > For now, I worked around this strange behavior by checking the count()
> > of the TransientHashSet backing my TransientOrderedSet implementation in
> > addition to contains().
>
> > But anyway: Is that behavior intended and facilitated internally
> > somehow? If so, is there some documentation about the rationale?
>
> > Bye,
> > Tassilo
>
> At first blush, the answer appears to be "no".
>
> Here is APersistentSet.contains:
>
> public boolean contains(Object key){
> return impl.containsKey(key);
>
> }
>
> Here is ATransientSet.contains:
>
> public boolean contains(Object key) {
> return this != impl.valAt(key, this);
>
> }
>
> This should probably use a sentinel; it's possible to put a transient
> map into itself, at least in principle. But the real problem:
>
> user=> (.valAt (.asTransient clojure.lang.PersistentHashMap/EMPTY) 1 42)
> nil
>
> Oops! This should have returned 42, not nil!
>
> The actual error is on line 278 of PersistentHashMap.java:
>
> Object doValAt(Object key, Object notFound) {
> if (key == null)
> if (hasNull)
> return nullValue;
> else
> return notFound;
> if (root == null)
> return null;
> return root.find(0, Util.hash(key), key, notFound);
>
> }
>
> This obviously should say
>
> if (root == null)
> return notFound;
>
> !!!
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