[issue39479] [RFE] Add math.lcm() function: Least Common Multiple
Tim Peters
report at bugs.python.org
Sat Feb 1 23:58:36 EST 2020
Tim Peters <tim at python.org> added the comment:
I'd have to hear back from Raymond more on what he had in mind - I may well have been reading far too much in the specific name he suggested.
Don't much care about API, etc - pick something reasonable and go with it. I'm not overly ;-) concerned with being "newbie friendly". If someone is in a context where they need to use probabilistic solutions, there is no substitute for them learning something non-trivial about them. The usual API for a Miller-Rabin tester supports passing in the number of bases to try, and it's as clear as anything of this kind _can_ be then that the probability of getting back True when the argument is actually composite is no higher than 1 over 4 to the power of the number of bases tried. Which is also the way they'll find it explained in every reference. It's doing nobody a real favor to make up our own explanations for a novel UI ;-)
BTW, purely by coincidence, I faced a small puzzle today, as part of a larger problem:
Given that 25 is congruent to 55 mod 10, and also mod 15, what's the largest modulus we can be certain of that the congruence still holds? IOW, given
x = y (mod A), and
x = y (mod B)
what's the largest C such that we can be certain
x = y (mod C)
too? And the answer is C = lcm(A, B) (which is 30 in the example).
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