Make Compose and Join optional in EdgeFunction

[fabianbs96]

Make the compose and join functions in the EdgeFunction implementations optional, if the IDETabulationProblem impl provides extend and combine.

Can we somehow emit a compile-time error, if neither are implemented?

[vulder]

About your question reg. the compile error. Am I missing something, or would not just a OR + concept check in a static assert be enough? If you wanna talk about the design just ping me :)

Btw. I added Sebi to check if this conflicts with our internal setup.

[vulder]

Inline should not really be needed here

[vulder]

@boehmseb Can you please double check if this change would work for us.

[fabianbs96]

The problem with concept+static_assert is that the Problem contains a virtual default implementation of extend and combine that forward to the EF-member-functions composeWith and joinWith. We would somehow need to statically detect that extend and combine have been overwritten.

I guess with the current design of IDETabulationProblem, this is not possible.

  virtual EdgeFunction<l_t> extend(const EdgeFunction<l_t> &L,
                                   const EdgeFunction<l_t> &R) {
    return L.composeWith(R); // <-- with the current design, this would emit a runtime error if compose() has
                             //     not been implemented *and* extend has not been overwritten
  }

  virtual EdgeFunction<l_t> combine(const EdgeFunction<l_t> &L,
                                    const EdgeFunction<l_t> &R) {
    return L.joinWith(R); // <-- similar possible runtime error as with compose
  }

Or do you have an idea, how one could detect that at compile time?