Not that I would understand any of this, but it works perfectly! Thank you so much Jens, Danny and Eli!
br, jukka > 2012/7/8 <jukka.tuomi...@finndesign.fi>: >> >> I came across this "mutable-define" by Eli (3+ years back)... >> >> ;; http://paste.lisp.org/display/67203 >> ;; this is a PLT version, translate as necessary >> >> (define-syntax-rule (define-mutable name expr) >> (begin (define b (box expr)) >> (define-syntax name >> (syntax-id-rules (set!) >> [(set! name new) (set-box! b new)] >> [(name . xs) ((unbox b) . xs)] >> [name (unbox b)])))) >> >> ;(define x 1) >> ;(define x 2) >> >> >> ...which seems beautifully concise for the job. The only problem is that >> it only seems to work in the interactions window in drracket. Is there a >> way to have it working inside a module? ... hopefully so that all the >> tweaks would take place inside the very module, rather than "required" >> from elsewhere (that would keep it an GP individual's property/"gene"). >> >> This is obviously what Danny is trying to explain me - "...language >> variant of Racket where "define" acts like redefinition at the module >> toplevel..." - but once again, I seem to be reaching out things before >> understanding them. > > Combining Dannys def and Eli's define-mutable I get this: > > > #lang racket > > ;; Returns true if stx is an identifier that's been lexically bound. > (define-for-syntax (lexically-bound? stx) > (let ([expanded (local-expand stx (syntax-local-context) #f)]) > (not (and (identifier? expanded) > (eq? #f (identifier-binding expanded)))))) > > (define-syntax (defm stx) > (syntax-case stx () > [(_ name expr) > (and (identifier? #'name) (lexically-bound? #'name)) > (syntax/loc stx (set! name expr))] > [(_ name expr) > (identifier? #'name) > (syntax/loc stx > (begin > (define b (box expr)) > (define-syntax name > (make-set!-transformer > (lambda (stx) > (syntax-case stx (set!) > [(set! name new) #'(set-box! b new)] > [(name . xs) #'((unbox b) . xs)] > [name #'(unbox b)]))))))])) > > ;;; Testing > > (defm x 1) > x > (list (+ x 40)) > (defm x 2) > x > (list (+ x 40)) > (set! x 3) > x > > > (defm y 4) > y > (list (+ y 40)) > (defm y 5) > y > (list (+ y 40)) > (set! y 6) > y > > > ; The output is > > 1 > '(41) > 2 > '(42) > 3 > 4 > '(44) > 5 > '(45) > 6 > > > -- > Jens Axel Søgaard > ____________________ Racket Users list: http://lists.racket-lang.org/users
