Simplified slot access in goops

["Maciek Godek" <pstrychuj@gmail.com>]

Hi,
Below is a simple set of functions and macros to make
the access to goops object properties easier:

(use-modules (oop goops))
(use-syntax (ice-9 syncase))

(define-syntax let-alias
  (syntax-rules ()
    ((_ ((id alias) ...) body ...)
     (let-syntax ((helper (syntax-rules ()
			    ((_ id ...) (begin body ...)))))
       (helper alias ...)))))

(define slot (make-procedure-with-setter slot-ref slot-set!))

(define-syntax in (syntax-rules ()
		    ((_ object expr ...)
		     (primitive-eval
		      (list 'let-alias
			    (map (lambda(s)(list(car s)(list 'slot object (list 'quote (car s)))))
				 (class-slots (class-of object)))
			    (quote expr) ...)))))

Now suppose we have an instance of a class:
(define-class C ()
  a b c)
(define o (make C))

Using the "in" macro, we can write:
(in o
  (set! a 5)
  (set! b (1+ a))
  (set! c (+ a b))
  (+ a b c))
=> 22

which is more convenient than:
(slot-set! o 'a 5)
(slot-set! o 'b (1+ (slot-ref o 'a))
(slot-set! o 'c (+ (slot-ref o 'a) (slot-ref o 'b)))
(+ (slot-ref o 'a) (slot-ref o 'b) (slot-ref o 'c))

Perhaps the possible inconvenience is that all variable
names that happen to be the slot names of a given class
are shadowed. In the long run it may also cause significant
performance problems (or that's what I think), especially
when dealing with objects with a hell lotta slots.

I wonder if it would be possible to make it optimizable
for the JIT compiler somehow (and to make the "in" syntax
official part of GOOPS)

Sincerely,
M.