> The goal is to define a data type by cases, where one can add new cases to the data type and new functions over the data type, without recompiling existing co

> The goal is to define a data type by cases, where one can add new cases to the data type and new functions over the data type, without recompiling existing code, and while retaining static type safety. Not sure what real problem this is solving. In practise you don't just add new cases, you delete some cases, and you re-add different cases later. Two different people might add two different cases in parallel with each other. Oops, now you have to re-compile anyway.