To be sure, I think we should consider keeping the old assumptions
syntax (.is_positive, Symbol(positive=True), etc.), but make them call
the new assumptions. This way, we will break very little
compatibility, and we will still have these useful shortcuts for the
simple cases.
Aaron Meurer
2011/12/7 Ondřej Čertík <ondrej.cer...@gmail.com>:
> On Wed, Dec 7, 2011 at 12:11 PM, krastanov.ste...@gmail.com
> <krastanov.ste...@gmail.com> wrote:
>>
>>
>> 2011/12/7 Ondřej Čertík <ondrej.cer...@gmail.com>
>>>
>>> On Wed, Dec 7, 2011 at 11:58 AM, Ronan Lamy <ronan.l...@gmail.com> wrote:
>>> > Le mercredi 07 décembre 2011 à 20:36 +0100, krastanov.ste...@gmail.com a
>>> > écrit :
>>> >> How should assumptions be used? More precisely why the following code
>>> >> does what it does
>>> >>
>>> >> In [18]: global_assumptions.clear()
>>> >>
>>> >> In [19]: x = Symbol('x', positive=True)
>>>
>>>
>>> ^^^ This is old assumptions, that will be eventually removed
>>>
>>> >>
>>> >> In [20]: ask(Q.positive(x)) # Why does it return None?
>>>
>>> New assumptions.
>>>
>>> >>
>>> >> In [21]: x > 0
>>> >> Out[21]: True
>>>
>>> Old assumptions.
>>>
>>> And so on. We need to write documentation how to use the new
>>> assumptions. I hit the same problems. Here is an example:
>>>
>>> + >>> from sympy import var, solve, S, refine, Q
>>> + >>> var("a z")
>>> + (a, z)
>>> + >>> f = z / (a**2+z**2)**(S(5)/2)
>>> + >>> solve(f.diff(z), z)
>>> + [-a/2, a/2]
>>> + >>> f.subs(z, a/2)
>>> + 16*sqrt(5)*a/(125*(a**2)**(5/2))
>>> + >>> refine(f.subs(z, a/2), Q.positive(a))
>>> + 16*sqrt(5)/(125*a**4)
>>>
>>> and we just need to document it well, then improve refine and other
>>> things, and then eventually remove the old assumptions.
>>
>> Does this mean that every instance of is_something must be changed to ask()?
>
> Eventually yes, but from my talks with Mateusz at the Google Mentor Summit,
> unfortunately it is not easy to do it step by step, because for various
> technical reasons one will have to remove the old assumptions in one step
> (and fix some solvers that depend on it).
>
>> Is it plausible in the meantime to have (is_something or ask(..))? Of course
>> in some cases 'or' wont be the correct operator.
>
> I think it is currently completely independent, and we should simply start
> using
> the new assumptions.
>
> Ondrej
>
> --
> You received this message because you are subscribed to the Google Groups
> "sympy" group.
> To post to this group, send email to sympy@googlegroups.com.
> To unsubscribe from this group, send email to
> sympy+unsubscr...@googlegroups.com.
> For more options, visit this group at
> http://groups.google.com/group/sympy?hl=en.
>
--
You received this message because you are subscribed to the Google Groups
"sympy" group.
To post to this group, send email to sympy@googlegroups.com.
To unsubscribe from this group, send email to
sympy+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/sympy?hl=en.
