[cells-devel] c-formula and setf

[Ramarren]

> A cell should be calculated by a
> formula if it isn't set to a value.

I think the easiest way to achieve that would be to just use two
cells, one c? and one c-in, and just have the former be equal to the
latter if it is set, and to some formula if it is not. If you really
want to have a consistent interface to the slot you should consider
overriding accessor methods.

Regards,
Jakub