On Thu, Apr 20, 2006 at 09:39:45AM +0200, Sebastian Egner wrote: > > Any ideas / suggestions on how to best approach this? > The usual approach is to turn a blind eye to the problem, > because most approaches that really solve it (like keeping > track of modifications) have inacceptable performance. > My approach would be to clearly state a general precondition > on hash tables: Hash tables assume that the values stored in > the table are not modified.
That is already stated, the problem being just that it severes the usefulness of eq? hash tables. > Another solution, e.g. in the Map type of the LEDA library > for C++, is to use the /pointer/ to the heap-allocated object > as a hash value. This is indeed the most efficient hash > function you can imagine. Unfortunately, this imposes the > severe constraint that the underlying garbage collector must > support this, e.g. by not moving objects in the heap. ... and you can't do it in standard RnRS Scheme, AFAIK. Panu -- personal contact: [EMAIL PROTECTED], +35841 5323835 technical contact: [EMAIL PROTECTED], http://www.iki.fi/atehwa/ PGP fingerprint: 0EA5 9D33 6590 FFD4 921C 5A5F BE85 08F1 3169 70EC
