BB-48: General user-defined types (beyond trivially copyable)

[mcmillan03]

General user types: Look at the HPEC'18 futures paper. For a generalized user type, we need to add methods to copy, create, and delete edges. Our user defined types today require that the type work with a memcopy. Our current approach is limited. Aydin has experimented with this for years and has never come up with a workable solution. Is there even a need for this? Can’t we cover most cases by using an integer key as the values in the GrB_matrix with that key points into a vector of user defined objects. But this doesn’t let you use the values referenced by the key in the GraphBLAS operations. A good example of when something like this might be needed is when processing strings.

[DrTimothyAldenDavis]

I've thought a lot about this too and don't have a good solution. RedisGraph creates property graphs without the need for variable-sized user-defined types. Adding variable-sized dynamic types to my library would be incredibly difficult for me to do. In my opinion this issue should be closed.