> Does this technique extend to polymophic types?
Yes, of course. The type F a b in the earlier message was polymorphic.
> Let's say we have the following type:
> > data D a = C | D a
> Is it possible to index the type D a?
I have just lifted the polymorphic Maybe -- which is isomorphic to
you
I admire the elegancy of your code which makes the changes to add new data
types minimum. There is one question I want to ask: Does this technique
extend to polymophic types?
Let's say we have the following type:
> data D a = C | D a
Is it possible to index the type D a? Or there is some fundmen
[EMAIL PROTECTED] wrote:
>
> ... loads of cunning stuff omitted
>
Software-engineering-wise your approach suffers
from an important weakness: a closed world assumption.
The programmer has to maintain your "TI" and pass it
on in all kinds of contexts for the array of types to
be handled. I also h
Throughout this message you imply, if not outright state, that Dynamics
requires unsafeCoerce/unsafePerformIO. This is simply not the case.
GHC implements Dynamics with unsafeCoerce, or did last time I checked,
but it can easily be implemented using only existentials. (I presume
that this decisio
