struct-like-classes

Common Lisp macro for classes defined with a DEFSTRUCT-like shorthand.

I use this in a few areas to save typing and to aid in live development (changing struct inheritance or layout in a running system with existing instances sometimes leads to badness only resolvable by deleting and recreating the packages containing the struct definitions -- possibly there are better ways to handle this, but this module is how I currently do it). I'm still undecided as to whether it's actually advisable to (incompletely) reproduce the functionality provided by DEFSTRUCT.

Thus, one can do:

(define-struct-like-class connection ()
  (server *server*)
  fd
  remote-peer
  remote-port
  forwarded-for)

instead of:

(defclass connection ()
  ((server :initform *server*
           :accessor connection-server)
   (fd :initform nil
       :accessor connection-fd)
   (remote-peer :initform nil
                :accessor connection-remote-peer)
   (remote-port :initform nil
                :accessor connection-remote-port)
   (forwarded-for :initform nil
                  :accessor connection-forwarded-for)))

(defgeneric connection-p (obj)
  (:method ((obj connection)) t)
  (:method ((obj t)) nil))

(defun copy-connection (obj)
  (make-instance-with-same-slots obj))

There's also a DEFINE-STRUCT-LIKE-BOUND-CLASS helper macro, which defines a struct-like class bound to a user-supplied symbol, a helper macro for binding the symbol, and helper functions for accessing slots of the currently-bound value.