A question about dynamic typing
Nick Name
nick.name@inwind.it
Sun, 19 Jan 2003 20:07:25 +0100
On Sun, 19 Jan 2003 12:50:16 -0600
Jon Cast <jcast@ou.edu> wrote:
> Short version: if
> Typeable is a super-class of Visible or mentioned in your existential
> type (i.e., forall a. (Visible a, Typeable a) => Con) you can use
> (fromDynamic . toDyn) to safely (attempt to) convert the abstract
> type into the concrete one. If that last paragraph wasn't coherent,
> I can try to explain it more.
Ok, this is clear. I am still not sure of how to decide the type to give
to the "extracted" object.
In the graphical interface, any object should have a menu saying on its
top row: "Text file" or "Applet" (depending from the type of the object)
and then a list of operations.
This should happen even when the object is inside the panel-list, (so
maybe a panel would be a list of untyped "objects" with an attribute of
type [Operation]).
But, to fully exploit the power of a "functionally-programmed" desktop,
the interface should allow the user to map an operation onto all the
objects of the panel; in this case the allowed operations should be
those that all the object share.
This is what I think, however I can't realize the connection between the
haskell type system and what I wish to have. Can someone lead me to a
clearer vision of the topic?
Vincenzo
--
First they ignore you, then they laugh at you,
then they fight you, then you win.
[Gandhi]