On Tue, Apr 5, 2016 at 12:01 PM, Michael Orlitzky <[email protected]> wrote:
> On 04/05/2016 01:03 PM, William Stein wrote:
>>
>> I think we should change is_prime for rational numbers, since people
>> get confused by this so much.
>>
>> How?  Pretty much any change at all would be better than the current
>> situation.  Options I can think of:
>>
>> - make is_prime([rational]) raise an error and tell the user what to do
>> - look at what is_prime([rational]) does in Pari, Mathematica, etc.,
>> and do the same thing
>> - make is_prime([rational]) return is_prime(ZZ([rational]))    -- this
>> would be a change that would potentially silently break some code, but
>> is what many people expect.
>>
>
> Why not have two? The problem is that everyone knows what is_prime() is
> supposed to do -- it's supposed to tell you if a number is prime. Except
> it doesn't always do that, it does some abstract mumbo jumbo whenever
> you don't have an integer (even if you do "have an integer").
>
> We could leave is_prime() for humans, and have is_prime_in_ring() for
> people who know what that means.

That would be much better than the current situation.

 -- William


-- 
William (http://wstein.org)

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