chickadee » describe-coops » describe-object

Generic procedure specialized on OBJ, responsible for printing the textual description of OBJ. describe calls this under the hood.

#;> (define-class <point> () (x y z))

#;> (describe <point>)
coops standard-class <point>
  class precedence list: (<standard-object>)
  slots: (x y z)

#;> (describe (make <point> 'x 1 'y 2 'z 3))
coops instance of class <point>:
  x : 1
  y : 2
  z : 3

#;> (define-method (describe-object (obj <point>) out)
      (fprintf out "<point> object with coordinates (~A, ~A, ~A)~%"
       (slot-value obj 'x) (slot-value obj 'y) (slot-value obj 'z)))

#;> (describe (make <point> 'x 1 'y 2 'z 3))
<point> object with coordinates (1, 2, 3)

If coops-primitive-objects is loaded, you can specialize on primitive objects such as fixnums; the default implementation prints both the object's class and the describe egg's description. For example:

#;> (describe 3)
exact integer 3 (#x3 #o3 #b11 #\x3)
#;> (use coops-primitive-objects)
#;> (describe 3)
coops instance of primitive class <fixnum>
exact integer 3 (#x3 #o3 #b11 #\x3)