Ronan Lamy wrote:
>> Why f.e. this variant:
>>
>> > h[2]>>> cos(x).series(x,1,n=2)
>> > (1 - x)*sin(1) + cos(1) + O((x - 1)**2)
>>
>> is bad ?
>
> What's bad is that '(x - 1)' in the O() is actually a symbol that's
> completely unrelated to x. This could be very confusing and it's
> unlikely that such an expression will be handled correctly by existing
> functions.
What's good is that only the user that reads the docstring is going
to be able to figure out how to do this. Anyone else is going to just
get the shifted function result. The commit message is also clear
about what's happening:
2) if sudo=True then return the expression with a non-functional
but proper looking O() term. Symbol trickery is used here to
replace x with Symbol(str(x-x0)) in the O() term.
> I agree that O() needs to be fixed to take an x0 argument before we
> can represent expansions at a point other than 0. Correct handling of all
> cases (x0 = oo, O(1, x, x0=0) + O(1, x, x0=1), ...) can probably wait.
Are you ok with proceeding, then? If not, could you clearly tell what it would
take to get a positive vote?
/c
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