type variables in constructors?

Question

Can I have a function in a data constructor? Like:

data Something = (a->b) Something1 Something2

Answer 1

Yeah, of course you can. The only important thing is that you (always) need a name for your data constructor:

data <name> <para0> <param1> ... = <constructor> <arg0> <arg1> <arg2> ...

So for our example, it becomes

data Something a b = Constructor (a -> b) Something1 Something2