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## Re: set-difference

 Re: set-difference From: Sam Steingold - 2004-10-30 15:00:39 ```> * Dan Starr [2004-10-30 10:05:39 -0400]: > > If it is known that both sets are sorted, the calculation can proceed > very quickly indeed. this is already outside ANSI CL. see CLOCC/CLLIB/sorted.lisp -- Sam Steingold (http://www.podval.org/~sds) running w2k ; ; ; ; ; There is Truth, and its value is T. Or just non-NIL. So 0 is True! ```

 set-difference From: Dan Starr - 2004-10-30 14:03:50 ```Concerning set-difference ... If it is known that both sets are sorted, the calculation can proceed very quickly indeed. Consider, apart from hashing, to write #'sorted-set-diff, which presumes sorting, and then use this on sorted sets. Intuitively, since decent sorting takes place in (* n (log n) time, and #'sorted-set-diff is one-pass, this could be a favorable solution for larger sets. Might compete favorably with hashing. It would require,however, two predicates: A :test parameter and a :pecedes parameter, so you might wind up inferring #'< from #'= and so forth. That could get sticky. Just a thought. Devious Dan ```
 Re: set-difference From: Sam Steingold - 2004-10-30 15:00:39 ```> * Dan Starr [2004-10-30 10:05:39 -0400]: > > If it is known that both sets are sorted, the calculation can proceed > very quickly indeed. this is already outside ANSI CL. see CLOCC/CLLIB/sorted.lisp -- Sam Steingold (http://www.podval.org/~sds) running w2k ; ; ; ; ; There is Truth, and its value is T. Or just non-NIL. So 0 is True! ```