How do I write a macro-defining macro in common li

问题:

I have about two macros (and climbing) in my codebase that look like this:

(defmacro def-stat-method (method-name stat)
  `(progn
     (defmethod ,method-name ((monster monster))
       (getf (stats monster) ,stat))
     (defmethod (setf ,method-name) (value (monster monster))
       (setf (getf (stats monster) ,stat) value))))

and this:

(defmacro def-energy-method (method-name stat)
  `(progn
     (defmethod ,method-name ((monster monster))
       (getf (energies monster) ,stat))
     (defmethod (setf ,method-name) (value (monster monster))
       (setf (getf (energies monster) ,stat) value))))

Each of the macros has the following calling syntax: (def-stat-method ranged-weapon :ranged-weapon)

I would like a macro (def-foo-method macro-name method) that expands into the appropriate macros so that (def-foo-method def-stat-method stats) expands into the first example above. I am a lisp newbie and don't really know how to do this. All help appreciated.

回答1:

Just write a macro that expands into another defmacro, like this:

(defmacro def-foo-method (macro-name method)
  `(defmacro ,macro-name (method-name stat)
     (let ((method ',method))
       `(progn
          (defmethod ,method-name ((monster monster))
            (getf (,method monster) ,stat))
          (defmethod (setf ,method-name) (value (monster monster))
            (setf (getf (,method monster) ,stat) value))))))

I think there might be a way to do this without the let, but nested backticks are confusing :)

回答2:

To me that code looks slow. An object-oriented runtime dispatch plus a search on a property list? Why?

Sometimes property lists are added to CLOS objects to provide storage for not often used slots or to make them easily extensible (where all kinds of properties could be added without knowing them all before running the program). Generally it might be better to make the properties real slots of the object.