(defvar *dimensions* nil)
(defvar *topology* :torus)
(defvar *ticks* nil)
+(defvar *breeds* nil)
-(defstruct turtle who color heading xcor ycor (label "") (label-color 9.9d0) (size 1d0))
+(define-condition stop nil nil)
+
+(defmacro with-stop-handler (&rest forms)
+ "MACRO WITH-STOP-HANDLER &rest FORMS => HANDLED-FORM
+
+ARGUMENTS AND VALUES:
+
+ FORMS: body to be handled
+ HANDLED-FORM: body with handling
+
+DESCRIPTION:
+
+ WITH-STOP-HANDLER is a convenience macro to handle when
+ programs issue a stop condition. When one does, a simple
+ :stop is returned."
+ `(handler-case (progn ,@forms) (stop (s) :stop)))
+
+(defstruct turtle who color heading xcor ycor (label "") (label-color 9.9d0) (size 1d0) shape)
(defstruct patch color xcor ycor)
(defun agentset-list (agentset)
(defun agent-p (o)
(or (turtle-p o) (patch-p o)))
+
+(defun breed-p (breed)
+ (find breed *breeds* :key #'car))
+
+(defun breed-default-shape (breed)
+ (second (find breed *breeds* :key #'car)))
+
+(defsetf breed-default-shape (breed) (shape)
+ `(setf (second (find ,breed *breeds* :key #'car)) ,shape))