On 29/08/2013 00:23, Mike Duigou wrote:
I am unsure what solution was used in Common Lisp (I think I knew once). The most likely solution for Java Collections would be to use a ThreadLocal<Boolean> which potentially recursive methods could check/set on entry and avoid recursing. Explicitly concurrent hostile implementations could use a plain boolean field rather than a ThreadLocal.
There are many problems with that, as you'd expect with anything involving ThreadLocal. Any use of threads (say the new Spliterable-related stuff) is going to have surprising behaviour. Callers have to be aware of global state, so may get incorrect answers (perhaps okay for logging, not so good for hashtables).
The problem is the APIs. Fiddling with internal implementation will just end in "cleverness".
Tom
