could you send me code that produces the failure, so I can debug it? Martin
On Wednesday, 4 February 2026 at 14:44:24 UTC+1 [email protected] wrote: > Some more details: > > - The problem is deterministic. So it is not a problem with my computer. > - I am trying to print the offending element. Unfortunately whatever I do > I always get "ValueError: invalid data to initialize a permutation". > Converting the element to a string (via str, or repr) does not give an > error but it does not give the full element (the string contains .... ). > > Not sure what to do. > > Best, > Michel > > > > > On Wednesday, February 4, 2026 at 1:01:39 PM UTC+1 Michel VAN DEN BERGH > wrote: > > > However when I turn the returned GAP representatives back into elements of > the Sage group (called "weyl_group") sometimes (very rarely) I get > > Traceback (most recent call last): > > > File "/home/vdbergh/TEX/ANYA/anya/scripts/p1xp1/compute_NCCR_orbit.py", > line 353, in <module> > test4("X8") > File "/home/vdbergh/TEX/ANYA/anya/scripts/p1xp1/compute_NCCR_orbit.py", > line 341, in test4 > compute_orbit(context, col) > File "/home/vdbergh/TEX/ANYA/anya/scripts/p1xp1/compute_NCCR_orbit.py", > line 41, in compute_orbit > w = weyl_group(w) ** -1 # left coset > ^^^^^^^^^^^^^ > File "sage/structure/parent.pyx", line 901, in > sage.structure.parent.Parent.__call__ > File "sage/structure/coerce_maps.pyx", line 164, in > sage.structure.coerce_maps.DefaultConvertMap_unique._call_ > File "sage/structure/coerce_maps.pyx", line 159, in > sage.structure.coerce_maps.DefaultConvertMap_unique._call_ > File "/home/vdbergh/sage/src/sage/groups/perm_gps/permgroup.py", line > 912, in _element_constructor_ > return self.element_class(x, self, check=check) > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > File "sage/groups/perm_gps/permgroup_element.pyx", line 518, in > sage.groups.perm_gps.permgroup_element.PermutationGroupElement.__init__ > ValueError: invalid data to initialize a permutation > > Anyone knows what could be the cause of this? > > Best, > Michel > > > > On Tuesday, February 3, 2026 at 7:22:01 PM UTC+1 Michel VAN DEN BERGH > wrote: > > On Tuesday, February 3, 2026 at 7:00:36 PM UTC+1 wrote: > > I don't know about efficient, but in the species code I use > libgap.RightTransveral(group, subgroup): > > def structures(self, *labels): > labels = _label_sets(self.parent()._arity, labels) > n = tuple([len(U) for U in labels]) > S = _SymmetricGroup(sum(n)).young_subgroup(n) > l = [e for l in labels for e in l] > if self._mc == n: > for rep in libgap.RightTransversal(S, self._dis): > yield tuple(S(rep)._act_on_list_on_position(l)) > > Does this help? > > Martin > > > Some quick experimenting seems to indicate that this is exactly what I > need! > > Thanks a lot! > > Michel > > > On Tuesday, 3 February 2026 at 14:25:12 UTC+1 wrote: > > Hi, > > I have a permutation group (a Weyl group in fact) and a subgroup given by > explicit generators. I would like to iterate over representatives for the > cosets of this group. Is there an efficient way to do this in Sage? > > I asked ChatGPT and it gave me all kinds of plausible looking commands, > none of which actually existed... > > Thanks! > > -- 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/7c1e3c6e-2a4a-47e6-999c-7db7fc8aa1c1n%40googlegroups.com.
