Hi !
I've been playing with libgap, which is great (I love the fact that lists
returned by GAP now start at 0...)
I have been unable, however, to elegantly work around the following simple
taks. Suppose:
sage: G= libgap.SymmetricGroup(3)
sage: g= libgap.eval("(1,2,3)")
sage: g in G # error
This does not work, to test membership. Unsatisfactory workarounds are:
(1) g in G.AsList()
works, but for large G this is VERY inefficient ! GAP is of course clever
at testing membership.
(2) use libgap.eval("G:= SymmetricGroup(3)") then libgap.eval("g:=
(1,2,3)") then libgap.eval("g in G")
This works, but well, in my real life example G and g are just not built
like that.
(3) best so far is
libgap.set_golobal("G", G)
libgap.set_global("g", g)
libgap.eval("g in G")
libgap.unset_global("G")
libgap.unset_global("g)
works, but is a bit long !
Is there a better way? in particular, is it possible to find the name which
G and g must have as variables within GAP? this used to be G.name() with
the old GAP interface. Maybe it doesn't make sense anymore.
I guess I could write a little GAP_membership(G, g) function, implememting
solution (3). It would work in general (eg, verifying whether g is in a
given conjugacy class, as returned by G.ConjugacyClasses() ).
thanks!
Pierre
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