In case you just want a permutation action of W on the cosets of G, you can avoid dealing with cosets all together. sage: f=libgap(W).FactorCosetAction(libgap(G)).Image() sage: f.OrbitLength(1) 138240
In fact, libgap(W).FactorCosetAction(libgap(G)) is a proper group homomorphism, so you can go back and forth between W and f. If you explain what you wanted to do with your coset representatives, I can say more... Dima On Thursday, February 5, 2026 at 6:15:17 AM UTC-6 [email protected] wrote: > Hmm I have to retract this last post.Using > > for i in range(0, len(R)): > w = W(R[i]) > > still triggers the bug. > > Best, > Michel > > > > > > > > > > On Thursday, February 5, 2026 at 12:57:16 PM UTC+1 Michel VAN DEN BERGH > wrote: > >> On Thursday, February 5, 2026 at 12:15:21 PM UTC+1 wrote: >> >> As a workaround, I think that explicitly converting the gap list returned >> by libgap.RightTransversal(W, G) into a python list helps. I.e., >> >> list(libgap.RightTransversal(W, G)) >> >> Martin >> >> >> I use this initially also for G=trivial (basically I am trying to >> incrementally build the stabilizer of something by iterating over the >> cosets of a stabilizing group already found) so constructing a list of >> which only a small part will be consumed is a bit inconvenient. However >> your issue suggests to use >> >> for i in range(0, len(R)): >> w = W(R[i]) >> >> This seems to work perfectly! >> >> I must say that I am mildly surprised that this works. I was guessing >> that the coset representatives would be found on the fly in some way. >> >> In any case: thanks for investigating and filing the issue! >> >> Best, >> Michel >> >> >> On Thursday, 5 February 2026 at 11:16:52 UTC+1 Martin R wrote: >> >> That's a huge example. >> >> sage: len(libgap.RightTransversal(W, G)) >> 138240 >> >> I think it is a gap bug, I am checking right now. >> >> >> On Thursday, 5 February 2026 at 07:46:47 UTC+1 wrote: >> >> > This is very strange code - you are attempting to change the variable >> of a loop inside a loop. >> > >> > What do you mean to do here? >> > >> > Dima >> >> Well that's not the point. Writing v=W(w) gives the same bug... >> >> Best, >> Michel >> >> PS. This was just some quick test code, but this being said, I think >> assigning to a loop variable is fine. This does not influence the state of >> the iterator. A quick test confirms this. >> >> >> >> >> -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/sage-support/7a342148-73e5-4bf4-861c-9ccc35e79929n%40googlegroups.com.
