Okay. Let me see if I understand this correctly: Let's say, hypothetically, that there were variables that worked exactly like fluids except that you could reference them by simply writing their names, instead of using (fluid-ref ...). Would those be what you want?
I was confusing our fluids and the (fluid-let ...) construct from MIT Scheme [0]. Are you looking for variables that behave the way fluid-let variables behave? (There's also a nice example on that page of how fluid-let works with continuations.) Best, Noah [0] http://www.gnu.org/software/mit-scheme/documentation/mit-scheme-ref/Dynamic-Binding.html On Tue, Mar 26, 2013 at 5:13 PM, Stefan Israelsson Tampe < stefan.ita...@gmail.com> wrote: > You need to combine fluids and dynamic-wind e.g., > > > (define guards (make-vector 10)) > (let lp ((i 0)) > (when (< i 10) (vector-set! guards i (make-fluid)))) > > (define-syntax with-special-soft > (lambda (x) > (syntax-case x () > ((_ (x ...) code ...) > (with-syntax (((((a k) ...) (y ...)) > (let loop ((i 0) (l #'(x ...)) (r '())) > (if (or (= i 10) (null? l)) > (list (reverse r) l) > (loop (+ i 1) (cdr l) (cons (car l) r)))))) > (with-syntax (((i ...) (iota (length #'(a ...))))) > (if (null? #'(y ...)) > #'(with-fluids (((vector-ref guards i) a) ...) > (with-special* ((i a k) ...) > code ...)) > #'(with-fluids (((vector-ref guards i) a) ...) > (with-special* ((i a k) ...) > (with-special-soft (y ...) code ...)))))))))) > > (define special-wind-guard (make-fluid (lambda (x) #t))) > (define-syntax-rule (with-special* ((i a k) ...) code ...) > (let ((last #f)) > (dynamic-wind > (lambda () > (set! last #f) > (when ((fluid-ref special-wind-guard) k) > (set! a (fluid-ref (vector-ref guards i)))) > ...) > (lambda () > (call-with-values (lambda () (begin code ...)) > (lambda ret > (set! last #t) > (apply values ret)))) > (lambda y > (unless last > (fluid-set! (vector-ref guards i) a) > ...))))) > > > On Tue, Mar 26, 2013 at 10:07 PM, Noah Lavine <noah.b.lav...@gmail.com> > wrote: > > Yes, I think parameters and fluids are the same. I was wondering if > > (with-redo-variables ...) could be a macro that expands to (with-fluids > > ...). Is that possible? It might not be. >
