Graph Adaptors

[neoblizz]

We need clarification on what needs to be done here?

[pratzl]

One use-case is to adapt a range-of-ranges structure to support the Graph Container Interface. An example is vector<vector<tuple<int,double>>>. I showed an example of the idea in ./graph-v2/example/CppCon2022. There are limits to the implementation, and a more general implementation would be needed.
There may be other use-cases.