[Types-sig] feedback: PyDL RFC 0.4

[Paul Prescod]

Tony Lownds wrote:
> 
> Why not allow a default type to a parameterized interface?
> 
> class (T:=Any) Set:
>  ...
> 
> decl f as def(x: Set)
> decl g as def(x: Set(Int))

Why ":=" and not just "="?

> Paul, is it your intention that...
> a tuple is a Sequence?
> a list can be a Record?
> 
> I hope so, I think these syntactic shortcuts will be good if so.

Yes, and yes. You could also define your own record types.

> Can one declare a Mapping of more than one pair of types?
> ie, {T1: T2, T3: T4}

Is this close enough:

{T1 or T3: T2 or T4}

I think that's closer to the mathematical concepts of domain and range.

> You dont show a way to specify default arguments. How about:
>
> def(Arg1: String, Arg2: String = optional) -> Int

Here are other ideas:

def(Arg1: String, Arg2: String?) -> Int

def(Arg1: String, [Arg2: String]) -> Int

 Paul Prescod