[cells-gtk-devel] Re: [cells-devel] Use of :initform c? and c-in

[Kenny Tilton]

Addendum.....

> Take the pill: Cells is Lotus 1-2-3 for slots of CLOS instances. Plus 
> a little twist:
>
> When a slot changes, Cells will call a generic function specializable 
> on the name of the slot and the types of the instance, new value, and 
> old value. Very handy, and I heard from a friend that Microsoft Excel 
> will call a VBA function or something when a spreadsheet cell changes. 
> Same idea: it is great to have a model working by itself, but how do 
> we get anything useful out of all those values changing automatically? 
> What if the "buy" flag on a stock goes to "on"? How do we arrange for 
> the damn stock actually to be bought? We need the option of a callback 
> where we can initiate an actual trade electronically. 

Last I looked, Cells-Gtk did not work much like a spreadsheet. Most 
slots (or more than I am used to) were c-input. Things still worked 
automatically, because Cells allows a change callback (defined by 
def-c-output) to SETF a c-input slot, but I for one try to avoid having 
things work that way because it loses some of the benefits of Cells. 
Most of them, actually. We are now back to a situation where the 
programmer has to figure out what things to SETF in a change callback. 
And we now no longer have a rule to look to for a slot, where we can see 
in one place the full algorithm for deciding a slot's value.

Anyway, my big long spreadsheet analogy might have folks who have seen 
only Cells-Gtk wondering what I am going on about, so I thought I should 
make this addendum. Everything I wrote is valid and it does explain the 
roles of c-input and c-formula, but Cells-Gtk may not feel very 
spreadsheet-y.

kt