On Tue, Sep 13, 2011 at 10:25 AM, Andrew Gwozdziewycz <apg...@gmail.com> wrote: > On Tue, Sep 13, 2011 at 9:54 AM, Panicz Maciej Godek > <godek.mac...@gmail.com> wrote: >> Hello, >> Is there any clever way of binding values to the list of unknown >> symbols in scheme? >> >> In common lisp there is a form "progv" that takes the list of symbols >> and their corresponding values and binds them within the body of >> progv. >> >> It is possible to do it using eval, like this: >> (define (bind-and-eval symbols values body) >> (eval `((lambda ,symbols ,body) . ,values) >> (interaction-environment))) >> (define-syntax let-symbols >> (syntax-rules () >> ((_ symbols values (body ...)) >> (bind-and-eval symbols values (quote (body ...)))))) >> >> but using eval for this just seems too heavy. Is there any way of >> doing it that would be more legal? >> >> Best regards, >> M. > > Seems likely that you could use `syntax-case' to create a `let` out of these: > > (define-syntax progv > (lambda (stx) > (define (create-bindings syms vals) > (datum->syntax stx (zip (syntax->datum syms) (syntax->datum vals)))) > (syntax-case stx () > ((_ symbols values body ...) > (with-syntax ((bindings (create-bindings #'symbols #'values))) > #'(let bindings > (begin body ...))))))) > > > > ;; usage > (progv (foo bar baz) (1 2 3) > (format (current-output-port) "Values: ~a ~a ~a\n" foo bar baz)) > ;; output: "Values: 1 2 3" > > Hope this helps! > > Andrew
I should point out that I'm using zip in srfi-1 (use-modules (srfi srfi-1)) -- http://www.apgwoz.com
