gene heskett <ghesk...@wdtv.com> wrote: > On Monday, December 12, 2011 12:44:27 PM Chris Angelico did opine: > > > On Tue, Dec 13, 2011 at 2:55 AM, Nick Dokos <nicholas.do...@hp.com> > wrote: > > > Terry Reedy <tjre...@udel.edu> wrote: > > >> calculations are helped by the fact that (a+b) % c == a%c + b%c, so > > > > > > As long as we understand that == here does not mean "equal", only > > > "congruent modulo c", e.g try a = 13, b = 12, c = 7. > > > > This is the basis of the grade-school "casting out nines" method of > > checking arithmetic. Set c=9 and you can calculate N%c fairly readily > > (digit sum - I'm assuming here that the arithmetic is being done in > > decimal); the sum of the remainders should equal the remainder of the > > sum, but there's the inherent assumption that if the remainders sum to > > something greater than nine, you digit-sum it to get the true > > remainder. > > > > (Technically the sum of the digits of a base-10 number is not the same > > as that number mod 9, but if you accept that 0 == 9, it works fine.) > > > > ChrisA > > And that is precisely the reason I have failed to understand why the 1-10
It's not clear from the above what you mean by "that is presicely the reason": what is "that"? > decimal system seems to have hung on for several hundred years when it is > clearly broken. > "broken" how? Thanks, Nick -- http://mail.python.org/mailman/listinfo/python-list
