A question about dynamic typing

[Nick Name]

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]