You can't create it without giving a variable, but you can easily do
Poly(1, x).get_domain(). There's probably a more direct way, though.
Aaron Meurer
On Fri, Jun 27, 2014 at 2:15 PM, Chris Smith <smi...@gmail.com> wrote:
> But you can't create a constant Poly without giving the domain. Try
> something like the following (and, again, trace the code to see if there is
> a more direct way of learning the domain):
>
>>>> Poly(1.2+var('x'))
> Poly(1.0*x + 1.2, x, domain='RR')
>>>> Poly(1+var('x'))
> Poly(x + 1, x, domain='ZZ')
>>>> Poly(1/S(3)+var('x'))
> Poly(x + 1/3, x, domain='QQ')
>>>> _.domain
> QQ
>
>
> On Friday, June 27, 2014 10:44:06 AM UTC-5, Aaron Meurer wrote:
>>
>> If you create a constant Poly, it picks the domain. You should look at
>> the source to see how it picks that.
>>
>> Aaron Meurer
>>
>> On Sat, Jun 21, 2014 at 10:48 AM, Christophe Bal <proj...@gmail.com>
>> wrote:
>> > Hello.
>> >
>> > I do not know if it is the case but I think that sympy should have a
>> > domain
>> > method for expressions. This will avoid error like for example float
>> > calculations raising to 1 for example that wi-ould not be a natural but
>> > a
>> > float.
>> >
>> > C.
>> >
>> >
>> > 2014-06-21 17:08 GMT+02:00 Saurabh Jha <saurab...@gmail.com>:
>> >
>> >> I think that makes sense. I think this functionality is already
>> >> implemented in Polys module in some form. I am not able to pin point
>> >> it.
>> >>
>> >>
>> >>>
>> >>> First, it' unnecessarily slow.
>> >>> Just check whether f == round(f) for floats.
>> >>>
>> >>> Second, the question whether a float is integral or not borders on
>> >>> madness - you never know whether the answer "it's a natural number"
>> >>> comes from the round-off lottery or is genuine.
>> >>>
>> >>> Third, regular expressions aren't going to give any meaningful results
>> >>> for symbolic expressions, and the "Sym" in SymPy defines its mission
>> >>> statement: symbolic math.
>> >>>
>> >>> If you pursue a way to find out whether a *symbolic expression* is in
>> >>> ZZ, QQ, Complex, or whatever, then that would be worth thinking about.
>> >>
>> >>
>> >>
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