On Fri, Apr 9, 2021 at 4:09 PM Vincent Delecroix <[email protected]> wrote: > > Thanks for the bug report. > > If you know how to proceed, please open a ticket and post the url here. > > - series goes through the ginac library (which is full of bugs and we > are trying to get rid off it)
more precisely, it's our fork of ginac, pynac, that is buggy, and it has diverged from ginac quite a bit, so it's unfair to blame ginac, the original upstream; unfortunately the people who used to develop pynac have more or less left the project. > - taylor goes through maxima which is much more reliable > > The sympy library offers a nice alternative for symbolic computations. > > Best > Vincent > > Le 09/04/2021 à 16:01, TBK a écrit : > > To Whom it May Concern: > > > > Per the "Reporting Bugs" procedure > > <https://doc.sagemath.org/html/en/developer/trac.html#reporting-bugs>, I am > > emailing sage-devel@ with a suspected bug. I am happy to open a TRAC > > ticket, if appropriate. > > > > I'm getting some seemingly incorrect series expansions. In particular, > > adding a constant is sometimes introducing an $x^{-1}$ term instead of an > > $x^0$ term. I have included below a fairly minimal repro. Sage correctly > > expands `(1-sqrt(1-x))/x`. However, sage insists that adding `123` > > introduces a `123*x^-1` term. Using `taylor()`, I get the expected > > expansion in both cases. > > > > This seems obviously incorrect, but I am new to sage so apologize if this > > is just pilot error. I looked for existing threads on power series bugs. > > The closest I found was this message > > <https://groups.google.com/g/sage-devel/c/_rB24fZSHKs/m/XneaemQ4AgAJ> > > asserting > > that the combinatorial species code has long been riddled with bugs. If > > this is a bug, is taylor() believed to be less bug-riddled? > > > > > > *Repro:* > > {{{ > > sage: ((1-sqrt(1-x))/x + 0).series(x,3) > > > > 1/2 + 1/8*x + 1/16*x^2 + Order(x^3) # correct > > sage: ((1-sqrt(1-x))/x + 123).series(x,3) > > > > 123*x^(-1) + 1/2 + 1/8*x + 1/16*x^2 + Order(x^3) # ??? > > # taylor() correctly expands both > > sage: taylor((1-sqrt(1-x))/x + 0,x,0,2) > > > > 1/16*x^2 + 1/8*x + 1/2 > > sage: taylor((1-sqrt(1-x))/x + 123,x,0,2) > > > > 1/16*x^2 + 1/8*x + 247/2 > > }}} > > > > *Version:* > > │ SageMath version 9.2, Release Date: 2020-10-24 │ > > │ Using Python 3.8.5. Type "help()" for help. │ > > *OS*: macOS Catalina (10.15.7) (64-bit x86) > > > > Best, > > Thomas > > > > > > -- > You received this message because you are subscribed to the Google Groups > "sage-devel" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/sage-devel/710d3756-f93a-731e-b945-a23b48fe9fe8%40gmail.com. -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-devel/CAAWYfq3mP8Bhd3FOLSVdPNfCAU2Dyn_DGV0fpSH_bGA_sQ_dXg%40mail.gmail.com.
