My mistake. You are correct that the two are equally efficient. It was an error in my timing test handler.
-- Peter Peter M. Brigham pmb...@gmail.com http://home.comcast.net/~pmbrig On Feb 15, 2015, at 7:56 AM, Dave Cragg wrote: > Peter, > > I don’t follow. If I change the repeat portion of your code to use repeat n > times as below, the speed doesn’t change. And the speed scales linearly in > both cases if the size of the data set is increased. > > put the keys of pList into indexList > put the number of lines of indexList into i > put i into numTimes > repeat numTimes times > -- tLine is never used, but "repeat for each" is faster than "repeat <n> > times" > -- and this iterates the correct number of times > put pList[i] & pDelim after outList > subtract 1 from i > end repeat > > The advantage of "repeat for each" is when iterating over chunks in a string. > (repeat for each line/item/word) In this case, we’re iterating over array > elements, and so there is no advantage. If you look back at my earlier > version which iterated through array elements from last to first, you’ll see > it is basically doing the same as your reverseSort, and the times are also > the same. > > Cheers > Dave > > >> On 15 Feb 2015, at 04:31, Peter M. Brigham <pmb...@gmail.com> wrote: >> >> Harking back to the original discussion on reversing a list -- still the >> subject of this thread, here's the original example as I saved it in my >> library. >> >> function reverseSort pList, pDelim >> -- reverse sorts an arbitrary list >> -- ie, item/line -1 -> item/line 1, item/line -2 -> item/line 2, etc. >> -- pDelim defaults to cr >> -- from an exchange on the use-LC list >> -- this was the fastest pure LC method of several proposed >> if pDelim = empty then put cr into pDelim >> split pList by pDelim >> put the keys of pList into indexList >> put the number of lines of indexList into i >> repeat for each line tLine in indexList >> -- tLine is never used, but "repeat for each" is faster than "repeat <n> >> times" >> -- and this iterates the correct number of times >> put pList[i] & pDelim after outList >> subtract 1 from i >> end repeat >> delete char -1 of outList >> return outList >> end reverseSort >> >> Note that the repeat is a "repeat for each line tLine…" even though the >> value of tLine is never actually used within the repeat loop. It's >> incredibly fast to do it that way, and it's an easy way to repeat something >> a foreseeable number of times. Using a "repeat n times" is glacial by >> comparison. I do agree that the dictionary should not just say the "repeat >> for each" form is much faster, it should say the "repeat for each" form is >> MUCH, MUCH faster. >> >> -- Peter >> >> Peter M. Brigham >> pmb...@gmail.com >> http://home.comcast.net/~pmbrig > > _______________________________________________ > use-livecode mailing list > use-livecode@lists.runrev.com > Please visit this url to subscribe, unsubscribe and manage your subscription > preferences: > http://lists.runrev.com/mailman/listinfo/use-livecode _______________________________________________ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
