I already gave my arguments why I don't think it's a good idea on the
issue page. Calling doit or series again is not that hard, and you
gain the ability to write such things, and also you don't get a
performance hit on automatic evaluation.
Aaron Meurer
On Mon, Mar 25, 2013 at 7:33 AM, Sergey Kirpichev <skirpic...@gmail.com> wrote:
> When creating a new object or modifying an already existing one, SymPy
> sometimes do some automatic evaluation. AFAIK, there is no formal rules,
> related to what is acceptable here and what is not (some thoughts and
> suggestions listed here [1]). For example, do we want to evaluate
> factorial(10000000)?
>
> Lets consider somewhat non-trivial example [2]. Mathematica does automatic
> series expansion if function arguments contains order term. For example:
> In[1]:= Tan[Series[Sin[x],{x,0,5}]]
> Out[1]=
> 3 5
> x x 6
> x + -- - -- + O[x]
> 6 40
> In[2]:= Tan[x] + O[x]^5
> Out[2]=
> 3
> x 5
> x + -- + O[x]
> 3
> In[3]:= Tan[x]*O[x]
> Out[3]=
> 2
> O[x]
>
> SymPy does only the last (but please note, that tan(x) + O(x) is evaluated
> to O(x)!). It looks inconsistent at best.
>
> The question: does it make sense for SymPy to be a more Mathematica-like
> here?
>
> References
> ========
>
> .. [1] https://github.com/sympy/sympy/wiki/Automatic-Simplification
> .. [2] http://code.google.com/p/sympy/issues/detail?id=3638
>
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