[Openmcl-devel] Redefining Mathematical Operators?

[Steven Núñez]

Greetings fellow Clozurians,

I have a legacy codebase in xlisp-stat and to run on CCL I need to redefine the mathematics operators to work on both numbers and lists. Ideally I'd be able to do something like this:

(defgeneric + (x y))
(defmethod + ((x number) (y number)) ...)	; Add x to y
(defmethod + ((x number) (y list)) ...)		; Add x to every element of y
(defmethod + ((x list) (y list)) ...)		; Add elements of x and y pairwise

However '+' isn't a generic function:

? (defmethod + ((x number) (y number)) t)
> Error: The function + is defined as something other than a generic function.
> While executing: ENSURE-GENERIC-FUNCTION, in process listener(1).

so I thought I would undefine it and then redefine it as a generic. Something like this:

(defparameter *+* #'+)		; Save + for later use
(fmakunbound '+)			; Undefine it so we can use a multi-method
(defgeneric + (x y))
(defmethod + ((x number) (y number))
  (funcall *+* x y))

But it looks like the '+' operator is used somewhere in the compiler:

? (defgeneric + (x y))
> Error: Undefined function + called with arguments (0 8) . signaled during assembly-time evaluation of form (+ 0 8)
> While executing: CCL::PARSE-X86-LAP-EXPRESSION, in process listener(1).

Has anyone got any ideas how to redefine these operators? I supposed a bit of macro-magic might do the trick, but I thought I'd ask here to see if anyone has done anything like this before and if there's anything I should watch out for if I have to go the macro route?

Regards,
	- Steve Nunez