On Tue, 10 Aug 2021 at 21:15, Simon Peyton Jones
wrote:
>
>
> I think you see why the instance sig must be at least as polymorphic ...
>
Thanks Simon, I do now see, but I'd have to say there's a heck of lot of
questions on StackOverflow (most not from me) being surprised/asking why.
See more
Ah, I see. Yes, you're right. Sorry.
On Tue, Aug 10, 2021, 3:15 PM Simon Peyton Jones
wrote:
> Do you have a concrete example?
>
>
>
> I think that the recursive calls will all go via the original class method
> with its original type – we can’t know that it’s calling **this**
> instance till
Do you have a concrete example?
I think that the recursive calls will all go via the original class method with
its original type - we can't know that it's calling *this* instance till much
later. So I still don't get it. An example would clear it up.
Simon
From: David Feuer
Sent: 10
Simon, there are times when a function has to be generalized to be made
polymorphic recursive. Perhaps the method takes an argument of type x (not
a class parameter), but to call itself, it needs to be able to take types
x, T x, T (T x), etc. That additional polymorphism can be introduced in the
It's hard to tell what is happening without a repro case. Can you share one?
You suggested that it might have something to do with using an operator. Does
the same thing happen if you replace the operator with an alpha-numeric name?
Simon
| -Original Message-
| From:
AntC,
I think you see why the instance sig must be at least as polymorphic than the
instantiated signature from the class - because that's what the client is going
to expect. We are building a record of functions, and they must conform to the
class signature.
I agree with David's (1) and (2)
