ranson@cnetlu.UUCP (Ranson) (12/02/88)
The CLOS specification (88-002R) seems to assume that it is possible to
define SETF methods with: (defun (setf foo) ...
I have never seen anything like that in the Steele book, and it does not
work with Allegro CL. Is it an extension being considered for ANSI Lisp?
Daniel Ranson
...!mcvax!inria!cnetlu!ransonccm@a.gp.cs.cmu.edu (Christopher McConnell) (12/04/88)
The CLOS spec is specifying how to define setf methods (as in CLOS methods with specializers) not the normal CL setf methods. So, you have to say (defmethod (setf woof) (value (object blah))). You use define-setf-method to define normal setf methods. --
barmar@think.COM (Barry Margolin) (12/06/88)
In article <3761@pt.cs.cmu.edu> ccm@a.gp.cs.cmu.edu (Christopher McConnell) writes: >The CLOS spec is specifying how to define setf methods (as in CLOS >methods with specializers) not the normal CL setf methods. So, you >have to say (defmethod (setf woof) (value (object blah))). You use >define-setf-method to define normal setf methods. No, that's not the answer. The calling sequence for such a method would be (setf <woof> <value> <blah>) and that is not the normal SETF syntax. CLOS needs a way for a class to customize the behavior of (setf (<slot-name> <object>) <value>) This is done by defining a method whose NAME is (setf <slot>), e.g. (defmethod (setf woof-frob) ((object woof) value) "Set the FROB slot of a WOOF." ...) For this to fit in well with the rest of the system, general support must be made for functions with names of the form (SETF <symbol>). For instance, after doing the above DEFMETHOD, (function (setf woof-frob)) should be valid. Such general support has been proposed within the ANSI committee (it has been bogged down for a while, mostly because of a controversy over whether this is really needed, and if so, whether SETF should be a special case or we should have a general, extendable "function spec" facility (as several Lisp systems do)). There are a couple of reasons why DEFINE-SETF-METHOD isn't good enough for this feature. The main problem is that we need names for these functions, not just a way to define them and get them. For example, GENERIC-FLET and GENERIC-LABELS also need to be able to bind these names. Barry Margolin Thinking Machines Corp. barmar@think.com {uunet,harvard}!think!barmar
ccm@a.gp.cs.cmu.edu (Christopher McConnell) (12/06/88)
I can only assume that you did not read my original post: >The CLOS spec is specifying how to define setf methods (as in CLOS >methods with specializers) not the normal CL setf methods. So, you >have to say (defmethod (setf woof) (value (object blah))). You use >define-setf-method to define normal setf methods. I stand by it. In the AAAI-88 copy of the CLOS specification: (defmethod (SETF WOOF) (value (object blah)) ...body) is the defined way to define a setf method that is executed for (setf (woof object) value). The parameter was moved to the begining to allow &rest to capture a list of reference args. You can also write specializers for the value as well. The comment about define-setf-method was meant to apply to the question of how you would define a setf function for a NORMAL LISP function, not a CLOS generic function. (Since he was trying to use DEFUN with the CLOS syntax, I assumed he was trying to apply the CLOS syntax to the problem of a normal setf function.) I agree that (function (SETF WOOF)) should return the setf function and should be allowed in CL. --