const_iterator it = const_splay_tree.find(a); //Splaying performed
would break usual de-facto thread-safety guarantees for STL and Intrusive containers (read-only access from different threads is thread-safe).
In other words, this is dangerous and misleading.
So the main question is: what approach do you think would be better? ¿Just splay in const operations and put a thread-safety warning? ¿Make const versions non-splaying? ¿Don't offer const versions of search functions?
Making the const versions non-splaying would destroy the functional equivalence between const and non-const search functions which might come as a surprise for programmers that did not read the documentation well. So i would opt for "don't offer const versions of search functions". IMO using iterator it = splay_tree.find(a, dont_splay);//No splay is superior. Kevin