13 | | I have a related question concerning `cartan_matrix`, and possibly `dynkin_diagram`. I was surprised that matrices indexed by `Z` and `N` are not implemented in sage and, similarly, that graphs with infinite vertex sets are not supported. It would be very easy to implement a fake Cartan matrix, say `C`, that given two integers make `C[i,j]`, or `C[i][j]`, return the corresponding entry of the Cartan matrix. Is some one able to tell me what functionality such a matrix would need in order to be useful to the root system code? Similarly, implementing a fake Dynkin diagram class would be straightforward as long as I knew what methods I have to implement. |

| 13 | I have a related question concerning `cartan_matrix`, and possibly `dynkin_diagram`. I was surprised that matrices indexed by `Z` and `N` are not implemented in sage and, similarly, that graphs with infinite vertex sets are not supported. It would be very easy to implement a fake Cartan matrix, say `C`, that given two integers makes `C[i,j]`, or `C[i][j]`, return the corresponding entry of the Cartan matrix. Is some one able to tell me what functionality such a matrix would need in order to be useful to the root system code? Similarly, implementing a fake Dynkin diagram class would be straightforward as long as I knew what methods I have to implement. |