Subject: Re: intersection From: Erik Naggum <erik@naggum.no> Date: 28 Jan 2004 23:11:33 +0000 Newsgroups: comp.lang.lisp Message-ID: <3284320293452997KL2065E@naggum.no> * Paul Dietz | If the lists are long enough, it becomes preferable to use a linear | time algorithm with eql hash tables. Yes, this is true, but I somehow expect a programmer who works with large sets to use a more efficient representation than lists. E.g., if the set has a finite number of candidate elements, a bit vector is a suitable representation, where UNION is implementable with BIT-IOR, INTERSECTION with BIT-AND, etc. I have no idea how long «long enough» is, though. You wouldn't have any empirical data on the threshold? -- Erik Naggum | Oslo, Norway 2004-028 Act from reason, and failure makes you rethink and study harder. Act from faith, and failure makes you blame someone and push harder.