From: Alan Gauld Date: 08/09/06 12:53:59 To: Kermit Rose; tutor@python.org Subject: Re: [Tutor] programming exercise in Python > # lenmult = len(mult) This is pretty redundant, it only saves two characters typing, you might as well do ****** hmm.... I had gotten in the habit of replacing potential multiple function calls and array references with variable name references acting from the hypothesis that variable name references take much less time than array referrences or function calls. I agree that in this case I did not need to do so. >>>>>>> for k in range(len(mult)): > # for k in range(lenmult): > # mult[k] = mult[k] + 1 > # if k == 0: > # if mult[k] == 1: > # mult[k] = 2 The whole of this bit only happens on the first time through the outer loop. The effect of it is to set mult[0] to 2 if its initial value was 0, so why not move it outside the loop and do: if mult[0] == 0: mult[0] = 1 Then the increment of the whole list will uplift it to 2 along with all the other increments. ****** Yes. I see that now. I did see that I asked the computer to do extra work by having it do work conditional of the initial value of k, but did not immediately see how to move that work outside the loop. >>>>>>>> > # testsum = 0 > # if k > 0: > # mult[k-1] = 0 > # for j in range(k,lenmult): > # testsum = testsum + mpylist[j][1] * mult[j] My brain is bending with this bit! I'm not sure if its right or not... I'm still not sure i understand what its trying to do... for k = 0, checks to see if it may add 1 to mult[0] for k = 1, sets mult[0] = 0, and checks to see if it may add 1 to mult[1] for k = 2, sets mult[1] = 0, and checks to see if it may add 1 to mult[2], etc >>>>>>>>>>>> > # if testsum < zlim: > # return mult > # mult[0] = -1 > # return mult But I think this can be better expressed as: if testsum >= zlim: mult[0] = -1 # failure condiotion return mult ***** The indentation did not survive repeated postings. .. if testsum < zlim: .. return mult .. mult[0] = -1 .. return mult if testsum < zlim I return mult if testsum >= zlim, I advance the k loop failure condition is that it get all the way through the k loop and not be able to increment mult. >>>>>>>>> As a matter of interest what does this bizarre algorithm accomplish in a practical sense? What is its purpose? I am truly intrigued... ******* :) The incr routine generates a vector of exponents to apply to the list mpylist [n] [0] m = product of mpylist [k] [0] ** mult[k] Another subroutine uses the number m in an algorithm I've devised, to find a divisor of the number z, from which I had calculated the critical value of zlim, and the mpylist vector. Experimentation will tell if this factor routine is as good as I would like it to be. Kermit < [EMAIL PROTECTED] >
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