Hi,

I'm trying to get my head around datatypes, and wondering how I might define a simple  "Task" datatype in Haskell.

data Task = Task { title :: String, completed :: Bool }

Ok, that's straightforward, but sometimes tasks become a list of tasks themselves

data Task = Task { title :: String, completed :: Bool, subtasks :: [Task] }

But that's not really right, because obviously, some tasks don't have subtasks. So I try this:

data Task = Task { title :: String, completed :: Bool } | TaskWithSubtasks { title :: String, completed :: Bool, subtasks :: [Task] }

It's a bit more accurate, but it's repeating things, which is ok with a simple type. Could anyone suggest a better way to define this? If I was using C#, which I'm far more familiar with, I could overload the constructor and refer to the smaller constructor. Is there a way to do that in Haskell, or am I still thinking too OOP?

Iain