What is the difference between using c-input (AKA c-in) and c-formula (AKA c?) in a slots :initform ?
The two define different kinds of cells: A c-input cell is a cell whose value may be set through explicit procedural code, using setf on the slot. Note: When the cell is referenced by other cells in a cells constraint network, setf-ing the cell causes the values of other cells to be recomputed. A c-formula cell is a cell whose value is obtained through evaluation of a formula. Note that the usual semantics of :initform do not apply when :initform is given by c-formula. Instead of just setting the value at initialization, the c-formula (generated from the supplied lisp form) specifies the dynamic relationship between the slot’s value and other aspects of the program state.
