If you want to override behaviour, why not just define a sum type wrapping other objects, a master function that matches on different cases, and then smaller fu

If you want to override behaviour, why not just define a sum type wrapping other objects, a master function that matches on different cases, and then smaller functions that decide on what to do for each case? That seems fine to me. Like this: type obj1 = { ... } type sum = | One of obj1 | Two of obj2 ... match param with | One obj -> f(obj) | Two obj -> f2(obj) ---- There is also the handle pattern which I've used with some success. You basically place some functions in a record/tuple and then call those functions when you need to. https://jaspervdj.be/posts/2018-03-08-handle-pattern.html https://jaspervdj.be/posts/2018-03-08-handle-pattern.html Edit: I mean to say that I've used something similar to the handle pattern in an immutable context (having a central function that takes objects that can be arbitrarily nested which carry their own function and data, and the parent object can call its function on a child object, and the child can call its function on its child, and so on...). Hopefully I am making sense.