Opened 13 years ago

Closed 13 years ago

Last modified 13 years ago

# problem with Abelian groups and trivial elements

Reported by: Owned by: ncalexan mabshoff major sage-duplicate/invalid/wontfix porting: Cygwin trivial abelian group class group ncalexan

### Description

This is a problem:

```sage: AbelianGroup(1, [1], names='e')
Trivial Abelian Group
sage: AbelianGroup(1, [1], names='e').list()
[]
```

The handling of 1's in the list of element orders is a problem:

```sage: AbelianGroup(3, [2, 1, 2], names=list('abc')).list()
---------------------------------------------------------------------------
<type 'exceptions.IndexError'>            Traceback (most recent call last)

/Users/ncalexan/Documents/School/MATH235/genus2cm/<ipython console> in <module>()

/Users/ncalexan/sage-2.10.3.rc3/local/lib/python2.5/site-packages/sage/groups/abelian_gps/abelian_group.py in AbelianGroup(n, invfac, names)
304     elif len(invfac) > n:
305         raise ValueError, "invfac (=%s) must have length n (=%s)"%(invfac, n)
--> 306     M = AbelianGroup_class(n, invfac, names)
307     return M
308

/Users/ncalexan/sage-2.10.3.rc3/local/lib/python2.5/site-packages/sage/groups/abelian_gps/abelian_group.py in __init__(self, n, invfac, names)
371         # *now* define ngens
372         self.__ngens = len(self.__invariants)
--> 373         self._assign_names(names)
374
375

/Users/ncalexan/Documents/School/MATH235/genus2cm/parent_gens.pyx in sage.structure.parent_gens.ParentWithGens._assign_names()

/Users/ncalexan/Documents/School/MATH235/genus2cm/parent_gens.pyx in sage.structure.parent_gens.normalize_names()

<type 'exceptions.IndexError'>: the number of names must equal the number of generators
```

This is the cause of strange things like:

```sage: x = ZZ['x'].gen()
sage: K
Number Field in a with defining polynomial x^4 + 4*x^2 + 2
sage: K = NumberField(x^4 + 4*x^2 + 2, 'a')
sage: K.class_group()
Class group of order 1 with structure  of Number Field in a with defining polynomial x^4 + 4*x^2 + 2
```

### comment:1 Changed 13 years ago by mhansen

• Resolution set to duplicate
• Status changed from new to closed

### comment:2 Changed 13 years ago by mabshoff

• Milestone changed from sage-2.11 to sage-duplicate/invalid
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