#18158: `__getitem__` for libGap_Element
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Reporter: vdelecroix | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-7.2
Component: interfaces | Resolution:
Keywords: | Merged in:
Authors: Vincent Delecroix | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/vdelecroix/18158 | c27056e7be55c28870ff781ff431b0fe58d927d5
Dependencies: | Stopgaps:
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Changes (by vdelecroix):
* milestone: sage-6.6 => sage-7.2
Old description:
> Some objects in GAP are not list but does support indexation
> {{{
> gap> S := SymmetricGroup(5);;
> gap> irr := Irr(S)[3];;
> gap> irr[1];
> 5
> }}}
> We provide in this ticket a generic `__getitem__` on `GapElement`.
New description:
Some objects in GAP are not PList but does support indexation
{{{
gap> S := SymmetricGroup(5);;
gap> irr := Irr(S)[3];;
gap> irr[1];
5
}}}
or
{{{
gap> gens := GeneratorsOfGroup(SL(2,GF(5)));;
gap> m := gens[1];;
gap> m[1];
[ Z(5), 0*Z(5) ]
gap> m[2];
[ 0*Z(5), Z(5)^3 ]
}}}
We change the way gap lists are detected and hence more objects are now
wrapped as `GapElement_List`.
--
Comment:
Replying to [comment:8 vbraun]:
> Getitem without length is IMHO useless. The GAP function `IsList` just
calls `IS_LIST` internally, so we should perhaps use that instead of
`IS_PLIST` to decide when to wrap it in a `GapElement_List`
Indeed it is much more robust and general. That way libgap vectors and
matrices are also considered as lists
{{{
sage: M = libgap.eval('SL(2,GF(5))').GeneratorsOfGroup()[1]
sage: M
[ [ Z(5)^2, Z(5)^0 ], [ Z(5)^2, 0*Z(5) ] ]
sage: M[0]
[ Z(5)^2, Z(5)^0 ]
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/18158#comment:10>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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