I'm having problems tracing the exact problem in my code: I have matrices of differential forms and at some point I get type errors.
Consider the following example:
class Test:
def __init__(self):
self.z = var('z')
self.U = CoordinatePatch([self.z])
self.D = DifferentialForms(self.U)
self.d = self.D.gens()
self.M = Matrix(self.D,2)
print self.M
self.M[0,0] = self.d[0]
print self.M
print (self.M.base_ring() is self.D)
The first instance works without error, from the second onward I get a type error:
┌────────────────────────────────────────────────────────────────────┐
│ SageMath version 7.5.1, Release Date: 2017-01-15 │
│ Type "notebook()" for the browser-based notebook interface. │
│ Type "help()" for help. │
└────────────────────────────────────────────────────────────────────┘
sage: load('bugtest.sage')
sage: Test()
[0 0]
[0 0]
[dz 0]
[ 0 0]
True
<__main__.Test instance at 0x1edc7cbd8>
sage: Test()
[0 0]
[0 0]
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-3-d1e5fd9e553c> in <module>()
----> 1 Test()
<string> in __init__(self)
/Applications/sage-7.5.1/src/sage/matrix/matrix0.pyx in sage.matrix.matrix0.Matrix.__repr__ (/Applications/sage-7.5.1/src/build/cythonized/sage/matrix/matrix0.c:11464)()
1664 """
1665 if self._nrows < max_rows and self._ncols < max_cols:
-> 1666 return self.str()
1667 if self.is_sparse():
1668 s = 'sparse'
/Applications/sage-7.5.1/src/sage/matrix/matrix0.pyx in sage.matrix.matrix0.Matrix.str (/Applications/sage-7.5.1/src/build/cythonized/sage/matrix/matrix0.c:13504)()
1876 rep = rep_mapping.get(x)
1877 else:
-> 1878 rep = repr(x)
1879 S.append(rep)
1880
/Applications/sage-7.5.1/src/sage/structure/sage_object.pyx in sage.structure.sage_object.SageObject.__repr__ (/Applications/sage-7.5.1/src/build/cythonized/sage/structure/sage_object.c:2691)()
190 return str(type(self))
191 else:
--> 192 result = repr_func()
193 if isinstance(result, unicode):
194 # Py3 compatibility: allow _repr_ to return unicode
/Applications/sage-7.5.1/local/lib/python2.7/site-packages/sage/tensor/differential_form_element.pyc in _repr_(self)
1006 format = DifferentialFormFormatter(self.parent().base_space())
1007 output = [format.repr(comp, fun) \
-> 1008 for (comp, fun) in self._components.items()]
1009 return ' + '.join(output)
1010
/Applications/sage-7.5.1/local/lib/python2.7/site-packages/sage/tensor/differential_form_element.pyc in repr(self, comp, fun)
161 [('d%r' % self._space.coordinate(c)) for c in comp])
162
--> 163 if fun == 1 and len(comp) > 0:
164 # We have a non-trivial form whose component function is 1,
165 # so we just return the formatted form part and ignore the 1.
/Applications/sage-7.5.1/src/sage/symbolic/expression.pyx in sage.symbolic.expression.Expression.__nonzero__ (/Applications/sage-7.5.1/src/build/cythonized/sage/symbolic/expression.cpp:17020)()
2574 return self.operator()(self.lhs().pyobject(), self.rhs().pyobject())
2575
-> 2576 pynac_result = decide_relational(self._gobj)
2577 if pynac_result == relational_undecidable:
2578 raise ValueError('undecidable relation: ' + repr(self))
/Applications/sage-7.5.1/src/sage/structure/element.pyx in sage.structure.element.Element.__add__ (/Applications/sage-7.5.1/src/build/cythonized/sage/structure/element.c:11198)()
1234 # Left and right are Sage elements => use coercion model
1235 if BOTH_ARE_ELEMENT(cl):
-> 1236 return coercion_model.bin_op(left, right, add)
1237
1238 try:
/Applications/sage-7.5.1/src/sage/structure/coerce.pyx in sage.structure.coerce.CoercionModel_cache_maps.bin_op (/Applications/sage-7.5.1/src/build/cythonized/sage/structure/coerce.c:10496)()
1105 # We should really include the underlying error.
1106 # This causes so much headache.
-> 1107 raise bin_op_exception(op, x, y)
1108
1109 cpdef canonical_coercion(self, x, y):
TypeError: unsupported operand parent(s) for '+': 'Algebra of differential forms in the variables z' and 'Integer Ring'
Maybe the symbolic variable is not "safe" inside a class?
