Re: Desirable macro

[Guy.Steele at CMU-10A]

I have often wanted a macro (call it FROTZ for now) that would do:
	(FROTZ + (CAR FIZZLEBLORT) TOOTSNOOTER)
   ==>  (SETF (CAR FIZZLEBLORT) (+ (CAR FIZZLEBLORT) TOOTSNOOTER))

(Actually, I would rather write
	((FROTZ +) (CAR FIZZLEBLORT) TOOTSNOOTER)
but such is life.)

People will readily see that FROTZ FOO is similar to the
"gets-foo" operator of Algol-like languages:
	A +:= B    means   A := A + B
	A *:= B    means   A := A * B

Of course, the combination FROTZ CONS already exists, and is
called PUSH.  But FROTZ is also useful with + and also with
ADJOIN or ADJQ:
	(DEFUN ADJOIN (X Y) (IF (MEMBER X Y) Y (CONS X Y)))
	(DEFUN ADJQ (X Y) (IF (MEMQ X Y) Y (CONS X Y)))
These are the "add-unique" or "add-to-set" operations.
	(DEFUN ADJPROP (X V Y) (FROTZ ADJQ (GET X Y) V))
(although there are more efficient ways to implement this
particular case).

So how about it?  And what to call it?  Actually, one could
compatibly call it PUSH (the three-arg case)!  But it would be wrong.
I can't think of anything else to call it.
--Guy