A month ago, I encountered a bug while using series. I used the
"Report a problem" link in the sage notebook to report it and never
got a reply. I couldn't find anything in trac either, so in order to
be sure that the problem is not lost, I repost it here once again. My
apologies if this turns out to be a duplicate ...
So:
var('q')
f=(q^13362120470/((q - 1)*(q^5 - 1)*(q^21 - 1)*(q^85 - 1)*(q^341 -
1)*(q^1365 - 1)*(q^5461 - 1)*(q^21845 - 1)*(q^87381 - 1)*(q^349525 -
1)*(q^1398101 - 1)*(q^5592405 - 1)*(q^22369621 - 1)*(q^89478485 -
1)*(q^357913941 - 1)*(q^1431655765 - 1)*(q^5726623061 - 1)) +
1)/(q^7635497409/((q - 1)*(q^5 - 1)*(q^21 - 1)*(q^85 - 1)*(q^341 -
1)*(q^1365 - 1)*(q^5461 - 1)*(q^21845 - 1)*(q^87381 - 1)*(q^349525 -
1)*(q^1398101 - 1)*(q^5592405 - 1)*(q^22369621 - 1)*(q^89478485 -
1)*(q^357913941 - 1)*(q^1431655765 - 1)*(q^5726623061 - 1)) + 1)
print f.series(q==0,2)
print f.subs(q=0)
f.series(q==0,2) gives Order(q^2). However, f.subs(q=0) gives 1. These
two results contradict each other. In fact, the series result is
false, whereas the subs result is correct.
Sorry for the large example, but smaller examples seem to work.
System information: I am using
ftp://ftp.sun.ac.za/pub/mirrors/www.sagemath.org/linux/64bit/sage-4.6.1-linux-64bit-ubuntu_8.04.4_lts-x86_64-Linux.tar.gz
on debian lenny.
regards,
Clemens Heuberger
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