Hi there! I'm using [selda](https://github.com/valderman/selda) package to deal with relational databases. This package represents database tables in haskell in a type-safe way. And to do so it leans on type operators. For example, here they are two different tables: ``` categories :: Table (RowID:*:Text) expenses :: Table (RowID:*:Text:*:Double:*:RowID) ``` As both of them belong to different types, I can't put them in a single list out of the box: ``` [categories, expenses] --- not valid!! ``` I'm aware of [different solutions](https://wiki.haskell.org/Heterogenous_collections) to deal with it, but they don't convince me: - Algebraic data types: I think in this situation it is specially a burden having to play type-switching... There can exist a lot of different table schemas and they may change at any moment. - Universal type: I see it as a kind of hack - Existential types: I have read that usually it is an anti-pattern, and in this case I don't understand how it should work, because types are constructed with `:*:` operator. So my question if it exists some natural way to treat types built with type operators as a single type. I have to recognize I don't understand well how all this stuff about type operators works. I have read something but I still don't get it. So any direction with it would be very gratifying, too :) Thanks in advance. Marc Busqué http://waiting-for-dev.github.io/about/