Common Lisp also provides type information, dynamic type information. CL-USER 72 > (defclass person () (name age)) #<STANDARD-CLASS PERSON 80101598FB>

Common Lisp also provides type information, dynamic type information. CL-USER 72 > (defclass person () (name age)) #<STANDARD-CLASS PERSON 80101598FB> I can now ask Lisp to find the class object named person. CL-USER 73 > (find-class 'person) #<STANDARD-CLASS PERSON 80101598FB> Now I've got a real class object, not just a pointer to dead code. I can inspect it, change it... I'm adding a slot to an existing class: CL-USER 74 > (defclass person () (name age height)) #<STANDARD-CLASS PERSON 80101598FB> I can then ask for the slots of that class. CL-USER 75 > (class-direct-slots (find-class 'person)) (#<STANDARD-DIRECT-SLOT-DEFINITION NAME 8220278CA3> #<STANDARD-DIRECT-SLOT-DEFINITION AGE 8220278CBB> #<STANDARD-DIRECT-SLOT-DEFINITION HEIGHT 8220278CD3>) I can define a method for it. CL-USER 76 > (defmethod greet ((a-person person)) (format t "Hello ~a" (slot-value a-person 'name))) #<STANDARD-METHOD GREET NIL (PERSON) 801001B69B> I now can retrieve the method object from its generic function. CL-USER 77 > (find-method #'greet () (list (find-class 'person))) #<STANDARD-METHOD GREET NIL (PERSON) 801001B69B> That's live code exploration using dynamic types. > You can do this with most major languages today as well. Hmm, I'm in this graphics program on my Mac, how do I "break" the program and then interact with its Objective-C objects?