#17246: FreeGroup(0)([]) broken
-------------------------+-------------------------------------------------
Reporter: darij | Owner:
Type: defect | Status: new
Priority: minor | Milestone: sage-6.4
Component: group | Keywords: gap, group, free group,
theory | border case
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
-------------------------+-------------------------------------------------
This is a border case, but I'd still prefer it to work:
{{{
sage: F = FreeGroup(0)
sage: F([])
---------------------------------------------------------------------------
ValueError Traceback (most recent call
last)
<ipython-input-47-49d58f580ab1> in <module>()
----> 1 F([])
/scratch/sage-6.4.beta2/local/lib/python2.7/site-
packages/sage/structure/parent.so in sage.structure.parent.Parent.__call__
(build/cythonized/sage/structure/parent.c:9603)()
/scratch/sage-6.4.beta2/local/lib/python2.7/site-
packages/sage/structure/coerce_maps.so in
sage.structure.coerce_maps.DefaultConvertMap_unique._call_
(build/cythonized/sage/structure/coerce_maps.c:4256)()
/scratch/sage-6.4.beta2/local/lib/python2.7/site-
packages/sage/structure/coerce_maps.so in
sage.structure.coerce_maps.DefaultConvertMap_unique._call_
(build/cythonized/sage/structure/coerce_maps.c:4163)()
/scratch/sage-6.4.beta2/local/lib/python2.7/site-
packages/sage/groups/free_group.pyc in _element_constructor_(self, *args,
**kwds)
808 P = x.parent()
809 except AttributeError:
--> 810 return self.element_class(self, x, **kwds)
811 if isinstance(P, FreeGroup_class):
812 names = set(P._names[abs(i)-1] for i in x.Tietze())
/scratch/sage-6.4.beta2/local/lib/python2.7/site-
packages/sage/groups/free_group.pyc in __init__(self, parent, x)
225 i=i+1
226 AbstractWordTietzeWord =
libgap.eval('AbstractWordTietzeWord')
--> 227 x = AbstractWordTietzeWord(l, parent._gap_gens())
228 ElementLibGAP.__init__(self, parent, x)
229
/scratch/sage-6.4.beta2/local/lib/python2.7/site-
packages/sage/libs/gap/element.so in
sage.libs.gap.element.GapElement_Function.__call__
(build/cythonized/sage/libs/gap/element.c:15598)()
ValueError: libGAP: Error, List Element: <list>[1] must have an assigned
value
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/17246>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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