# 'CyclicCode_with_category' object has no attribute 'gen_mat'

I am trying to create the generator matrix for Quadratic Residue code and the code I am using is:

```
def gen_matrices(n):
C = codes.QuadraticResidueCode(n, GF(2))
D = C.dual_code()
G = C.gen_mat()
H = D.gen_mat()
J = G.transpose() * (G * G.transpose())^-1
K = H.transpose() * (H * H.transpose())^-1
if rank(block_matrix([[G],[H]]))!=G.ncols()\
or G * H.transpose ()!=0:
raise("Logic error: The code is not LCD")
return [ G, H, J, K ]
gen_matrices(17)
```

Here I am first generating the QR code, where G is the generator matrix for the code C and H is the generator matrix for the cyclic code D. So after the encoding is done we now do XOR operation of the two codes - z = xG (XOR) yH. Now I want to do decoding and here J and K are the matrices which are used for doing decoding. Here J is given by J = G.Transpose*(G*G.Transpose)^-1.

Here I am running a code that is being used in a paper. The paper is (https://hal.archives-ouvertes.fr/hal-01240242/document (https://hal.archives-ouvertes.fr/hal-...)).

When I am running the code I am getting the following error:

```
AttributeError Traceback (most recent call last)
<ipython-input-2-68b96fb2983c> in <module>()
----> 1 gen_matrices(Integer(17))
<ipython-input-1-f09fbcf52b0e> in gen_matrices(n)
2 C = codes.QuadraticResidueCode(n, GF(Integer(2)))
3 D = C.dual_code()
----> 4 G = C.gen_mat()
5 H = D.gen_mat()
6 J = G.transpose() * (G * G.transpose())**-Integer(1)
/opt/sagemath-8.1/src/sage/structure/category_object.pyx in sage.structure.categ ory_object.CategoryObject.__getattr__ (build/cythonized/sage/structure/category_ object.c:8014)()
854 AttributeError: 'PrimeNumbers_with_category' object has no a ttribute 'sadfasdf'
855 """
--> 856 return self.getattr_from_category(name)
857
858 cdef getattr_from_category(self, name):
/opt/sagemath-8.1/src/sage/structure/category_object.pyx in sage.structure.categ ory_object.CategoryObject.getattr_from_category (build/cythonized/sage/structure /category_object.c:8177)()
869 cls = self._category.parent_class
870
--> 871 attr = getattr_from_other_class(self, cls, name)
872 self.__cached_methods[name] = attr
873 return attr
/opt/sagemath-8.1/src/sage/cpython/getattr.pyx in sage.cpython.getattr.getattr_f rom_other_class (build/cythonized/sage/cpython/getattr.c:1837)()
247 dummy_error_message.cls = type(self)
248 dummy_error_message.name = name
--> 249 raise dummy_attribute_error
250 cdef PyObject* attr = _PyType_Lookup(<type>cls, name)
251 if attr is NULL:
AttributeError: 'CyclicCode_with_category' object has no attribute 'gen_mat'
```

Can anyone please suggest what I need to do?

Please provide a complete reproducible example, that others can copy-paste to study your problem.

There are indentation problems in the code for the function definition in the question.

The way to call the function to obtain the quoted error message is also missing.

Thanks for your edits to the question. With code to reproduce the error, debugging is a pleasure.