On Sep 9, 8:15 pm, "J. Cliff Dyer" <[EMAIL PROTECTED]> wrote: > Dotan Cohen wrote: > > FIrst of all, how is the % symbol (as in 70%6=4) called in English? > > > Second, in Turbo C -111%10=-1 however in python -111%10=9. Is one or > > the other in error? Is this a known gotcha? I tried to google the > > subject however one cannot google the symbol %. Thanks in advance. > > > Dotan Cohen > > The % operator is called "modulo" in English. I don't think the > difference in implementation is an error. It's just a difference of > calculation method. > > Python will always yield a number x = m%n such that 0 <= x < n, but > Turbo C will always yield a number such that if x = m%n -x = -m%n. That > is, since 111 % 10 = 1, -111 % 10 = -1. The two values will always > differ by n (as used above). > > I'm sure there are mathematicians on the list who can give you a more > technical, precise explanation of the reasons for the different results.
I don't know if there's a mathematical explanation of the difference, but I prefer the behaviour of the Python modulo operator because for any a, b, n, if a = b (mod n) holds then the Python expression 'a % n == b % n' evaluates to True. -- Arnaud -- http://mail.python.org/mailman/listinfo/python-list