#10452: Weird behaviour with cusps
-----------------------------+----------------------------------------------
Reporter: davidloeffler | Owner: craigcitro
Type: defect | Status: new
Priority: major | Milestone: sage-4.6.2
Component: modular forms | Keywords: cusps
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
-----------------------------+----------------------------------------------
The command "reduce_cusp" seems to be a bit flaky -- here are two
perfectly standard inputs that cause it to fail in different ways:
{{{
sage: G = Gamma1(5); G
Congruence Subgroup Gamma1(5)
sage: G.reduce_cusp(1/2) # works
1/2
sage: G.reduce_cusp(3) # boom (1)
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/home/masiao/<ipython console> in <module>()
/usr/local/sage/sage-4.6/local/lib/python2.6/site-
packages/sage/modular/arithgroup/congroup_gammaH.pyc in reduce_cusp(self,
c)
658 """
659
--> 660 return self._reduce_cusp(c)[0]
661
662 def _reduce_cusp(self, c):
/usr/local/sage/sage-4.6/local/lib/python2.6/site-
packages/sage/modular/arithgroup/congroup_gammaH.pyc in _reduce_cusp(self,
c)
725 if d == 1:
726 if v in H:
--> 727 return Cusps((0,1)), 1
728 if (N-v) in H:
729 return Cusps((0,1)), -1
/usr/local/sage/sage-4.6/local/lib/python2.6/site-
packages/sage/structure/parent.so in sage.structure.parent.Parent.__call__
(sage/structure/parent.c:6462)()
/usr/local/sage/sage-4.6/local/lib/python2.6/site-
packages/sage/structure/coerce_maps.so in
sage.structure.coerce_maps.DefaultConvertMap_unique._call_
(sage/structure/coerce_maps.c:3118)()
/usr/local/sage/sage-4.6/local/lib/python2.6/site-
packages/sage/structure/coerce_maps.so in
sage.structure.coerce_maps.DefaultConvertMap_unique._call_
(sage/structure/coerce_maps.c:3021)()
/usr/local/sage/sage-4.6/local/lib/python2.6/site-
packages/sage/rings/integer.so in sage.rings.integer.Integer.__init__
(sage/rings/integer.c:7312)()
TypeError: unable to coerce <type 'tuple'> to an integer
sage: G.reduce_cusp(oo) # boom (2)
---------------------------------------------------------------------------
AttributeError Traceback (most recent call
last)
/home/masiao/<ipython console> in <module>()
/usr/local/sage/sage-4.6/local/lib/python2.6/site-
packages/sage/modular/arithgroup/congroup_gammaH.pyc in reduce_cusp(self,
c)
658 """
659
--> 660 return self._reduce_cusp(c)[0]
661
662 def _reduce_cusp(self, c):
/usr/local/sage/sage-4.6/local/lib/python2.6/site-
packages/sage/modular/arithgroup/congroup_gammaH.pyc in _reduce_cusp(self,
c)
695 N = int(self.level())
696 Cusps = c.parent()
--> 697 v = int(c.denominator() % N)
698 H = self._list_of_elements_in_H()
699
/usr/local/sage/sage-4.6/local/lib/python2.6/site-
packages/sage/structure/element.so in
sage.structure.element.Element.__getattr__
(sage/structure/element.c:2666)()
/usr/local/sage/sage-4.6/local/lib/python2.6/site-
packages/sage/structure/parent.so in
sage.structure.parent.getattr_from_other_class
(sage/structure/parent.c:2840)()
/usr/local/sage/sage-4.6/local/lib/python2.6/site-
packages/sage/structure/parent.so in
sage.structure.parent.raise_attribute_error
(sage/structure/parent.c:2638)()
AttributeError: 'PlusInfinity' object has no attribute 'denominator'
}}}
In each case {{{ G.reduce_cusp(Cusp(...)) }}} gives the right answer, so
the problem is apparently that various code expects the input to be a Cusp
object and raises problems when it isn't.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10452>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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