How to Specify the Type of a Class Slot

Asked Jul 02 '19 at 05:19

Active Jul 02 '19 at 05:19

Viewed 33 times

What is the meaning of the :type type-specifier on a slot in a defclass expression? It doesn't seem to work the same way as in defstruct:

* (defclass counter ()
    ((value :initform 0
            :type (integer 0 *)
            :accessor value)))
#<STANDARD-CLASS COMMON-LISP-USER::COUNTER>
* (defparameter *c* (make-instance 'counter))
*C*
* (value *c*)
0
* (decf (value *c*))
-1
* (value *c*)
-1

Why does (decf (value *c*)) not produce an error?

asked Jul 02 '19 at 05:19

davypough

1,847
11
21

1

http://www.sbcl.org/manual/#Declarations-as-Assertions – coredump Jul 02 '19 at 06:29
2

How to force slot's type to be checked during make-instance? https://stackoverflow.com/questions/51723992/how-to-force-slots-type-to-be-checked-during-make-instance – Rainer Joswig Jul 02 '19 at 08:29
2

Consequences undefined (http://www.lispworks.com/documentation/HyperSpec/Body/m_defcla.htm) – Spenser Truex Jul 02 '19 at 09:34

How to Specify the Type of a Class Slot

0 Answers0