Fun idea: Dynamically generated structs

[ivanperez-keera]

I'm trying to link Copilot inside Ogma so that users don't have to execute runhaskell.

I'm finding a limitation: Ogma reads a data structure definition from a C file, and can currently generate the equivalent in Haskell. However, of Ogma runs Copilot for the user, then that struct would have to be generated dynamically.

I think this can be done with heterogeneous lists and some datatype representing dynamic structs. We'd lose some type safety along the way, but Ogma could guarantee that it generates code that always uses structs correctly, so I expect that not to be a problem.

If anybody has a clear idea of how this could be done, that'd really help.

[RyanGlScott]

My attempt at defining dynamically typed structs can be found in this gist. The key data type is DynStruct:

data DynStruct (name :: Symbol) (fields :: [(Symbol, Type)]) -- Exported abstractly

Along with a withDynStruct function that computes a DynStruct value without needing to know the name or fields of the struct statically:

withDynStruct :: String -> [Value ()] -> (forall name fields. DynStruct name fields -> r) -> r

If Ogma were to use this, then all Ogma would have to do is compute the struct name at runtime, as well as the Values corresponding to the struct fields. I haven't looked closely at the part of Ogma that needs this code, so it is possible that there are some design considerations that I am overlooking. How does something like this look?