New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

An unspecified power of x is reported to be `O(log(x)**6)` #14384

normalhuman opened this Issue Mar 4, 2018 · 3 comments


None yet
3 participants
Copy link

normalhuman commented Mar 4, 2018

>>> var('x a')
>>> series(x**a, x, 0)

This should probably return the expression x**a itself, as x**a is not O(log(x)**6) when a is negative.

@normalhuman normalhuman added the series label Mar 4, 2018

skirpichev added a commit to skirpichev/diofant that referenced this issue Mar 4, 2018


This comment has been minimized.

Copy link

ArighnaIITG commented Mar 7, 2018

@normalhuman ,
I was trying to decipher the series function in sympy.core.expr in order to solve this issue.
Some questions are coming up ::

I believe this particular function call goes to the n-series handling part of the function -
In that , we have

if n is not None:  # nseries handling
       s1 = self._eval_nseries(x, n=n, logx=logx)
        o = s1.getO() or S.Zero

Is the _eval_nseries here being called from the Pow class in sympy.core.power?
And what checkpoints do we provide? Like when a is not explicitly specified, we return the sympified expression, without any order evaluation.
Is Pow the only case?


This comment has been minimized.

Copy link

normalhuman commented Mar 7, 2018

It's not about adding a checkpoint like "if the expression is Pow, and the exponent is a symbol, and the sign of symbol is unknown, then..." The goal isn't to special-case this particular function; it is to understand and improve the algorithm for computation of power series.


This comment has been minimized.

Copy link

bibhu107 commented Jul 21, 2018

I am new to sympy and Open Source. I feel this issue interesting, If @skirpichev Is not doing can I take it?

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment