On Sun, Mar 4, 2012 at 2:35 AM, Chris Smith <smi...@gmail.com> wrote:
>
>
> On Sun, Mar 4, 2012 at 10:39 AM, prateek papriwal
> <papriwalprat...@gmail.com> wrote:
>>
>> so somehow we need to merge nsimplify() method into sqrt() method .
>>
>> in that case when we call sqrt(4.41)
>>
>> automatically sqrt(nsimplify(4.41,rational=True)) will be called .
>>
>>
>
> Since 4.41 is a Float, we don't assume that it is an exact number so the
> conversion happens (as Aaron is noted) upon instantiation of the sqrt and
> 2.1 is returned. If you know the 4.41 is exact you can enter it as a string
> to Rational:
>
> >>> sqrt(Rational('4.41'))
> 21/10
>
> Also, it seems the following could be added to Pow:
>
> def _eval_is_rational(self):
> p = self.func(*self.as_base_exp()) # in case it's unevaluated
> if not p.is_Pow:
> return p.is_rational
> b, e = p.as_base_exp()
> if e.is_Rational and not e.is_Integer and b.is_Rational:
> return False
>
> This would allow False to be returned for sqrt(3).is_rational (or True for
> is_irrational).
+1 to that.
Aaron Meurer
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