Jon Pretty

You always care about the asymptotic properties of your data structures. So there is never a case where Seq makes sense, even as a concept!

In the case of map, flatMap, filter and foldLeft the complexity is the same for List and Vector, and you can solve a lot of problems with just these operations.

But even if you do just want these operations, you’re far better off with a typeclass rather than sub typing.

Citation needed.

flatMap on List suspiciously allows the function parameter to return something that is not a List.

I saw this for the first time in our code base the other day. List flatmapping with Option return type. Did a double take until I realised it was the inheritance that allows it... so is this breaking the monadic laws? I suppose not if you start with the base type but yes for List

actually thinking about it, it feels more like an extension to the monad than a contravention of its laws

It's analogous to saying that the `|+|` operation on a monoid should allow the composition of different types. In other words, it is LITERALLY the same as claiming that we should be able to write `1 + "2"` and expect meaningful coercion.