Determining which Plots Are Linked

Determining who is linked is handled by two messages, :linked and :links.

:linked

(send p :linked) returns T if p is linked, NIL if not.

(send p :linked t) links p.

(send p :linked nil) unlinks p.

This method must set an internal flag indicating whether a plot is linked, so an override must use call-next-method.

:links

(send p :links) returns NIL if p is not linked. If p is linked, it should return a list of all plots linked to p. The list may, but need not, include p.