That "syntax-rules" is of course syntax-case. Try writing it first with unhygienic macros and get that working before porting to syntax-case if you don't know the ins-and-outs of syntax-case.
-- Linus Björnstam On Mon, 5 Apr 2021, at 14:21, Linus Björnstam wrote: > Can you use the procedural part of syntax-rules? You have the power of > using scheme at expansion time, which means you could do list-ref all > you want. > > The only thing is that guile lacks syntax->list, so sometimes you have > to manually turn it into a list. Say you are matching ((_ stuff ...) > Body) stuff is a syntax object. You could turn it into a list of syntax > objects by doing #'(stuff ...). Then you can treat it as a regular > list, and use quasisyntax to put it back into your output syntax. > > Writing this on my phone. Sorry for the brevity (and lack of code). > > -- > Linus Björnstam > > On Mon, 5 Apr 2021, at 13:30, Dr. Arne Babenhauserheide wrote: > > Hi, > > > > In dryads-wake I need selection of the element in a list in a macro from > > user-input. Currently I have multiple macros, and the correct one (which > > strips the non-selected choices) is selected in a simple cond: > > > > (define-syntax-rule (Choose resp . choices) > > "Ask questions, apply consequences" > > (cond > > ((equal? resp 1) ;; resp is user-input. It is a natural number. > > (Respond1 choices)) > > ((equal? resp 2) > > (Respond2 choices)) > > ((equal? resp 3) > > (Respond3 choices)) > > (else > > #f))) > > > > For this however I have three syntax-case macros: > > > > (define-syntax Respond1 > > (lambda (x) > > (syntax-case x () > > ((_ ((question consequences ...) choices ...)) > > #`(begin > > (respond consequences ...))) > > ((_ (choices ...)) > > #`(begin #f))))) > > > > (define-syntax Respond2 > > (lambda (x) > > (syntax-case x () > > ((_ (choice choices ...)) > > #`(begin > > (Respond1 (choices ...)))) > > ((_ (choices ...)) > > #`(begin #f))))) > > > > (define-syntax Respond3 > > (lambda (x) > > (syntax-case x () > > ((_ (a b choices ...)) > > #`(Respond1 (choices ...))) > > ((_ (choices ...)) > > #`(begin #f))))) > > > > > > I would like to get rid of those three definitions and replace them by > > at most two (one that strips N initial list entries, and Respond1). > > > > I cannot move to procedures, because I have code that must be executed > > only during final processing, and when I evaluate any of the > > consequences (as it happens with procedure-arguments), then the timing > > of the code execution does not match anymore. So I must absolutely do > > this in macros. > > > > > > I’ve tried to get that working, but all my tries failed. Is there a way > > and can you show it to me? > > > > This is a minimal working example. The output should stay the same, > > except for part 4, which needs this change to work (see at the bottom), > > but I would like to: > > > > - replace Respond2 and Respond3 by something recursive, so resp can have > > arbitrary high values (not infinite: max the length of the options) and > > - replace the cond-clause by a call to the recursive macro. > > > > (define-syntax-rule (respond consequence consequence2 ...) > > (begin > > (write consequence) > > (when (not (null? '(consequence2 ...))) > > (write (car (cdr (car `(consequence2 ...)))))))) > > > > (define-syntax Respond1 > > (lambda (x) > > (syntax-case x () > > ((_ ((question consequences ...) choices ...)) > > #`(begin > > (respond consequences ...))) > > ((_ (choices ...)) > > #`(begin #f))))) > > > > (define-syntax Respond2 > > (lambda (x) > > (syntax-case x () > > ((_ (choice choices ...)) > > #`(begin > > (Respond1 (choices ...)))) > > ((_ (choices ...)) > > #`(begin #f))))) > > > > (define-syntax Respond3 > > (lambda (x) > > (syntax-case x () > > ((_ (a b choices ...)) > > #`(Respond1 (choices ...))) > > ((_ (choices ...)) > > #`(begin #f))))) > > > > > > (define-syntax-rule (Choose resp . choices) > > "Ask questions, apply consequences" > > (cond > > ((equal? resp 1) > > (Respond1 choices)) > > ((equal? resp 2) > > (Respond2 choices)) > > ((equal? resp 3) > > (Respond3 choices)) > > (else > > #f))) > > > > > > (display "Choose 1: should be bar:") > > (Choose 1 (foo 'bar) (foo 'war 'har) (foo 'mar) (foo 'tar)) > > (newline) > > (display "Choose 2: should be warhar:") > > (Choose 2 (foo 'bar) (foo 'war 'har) (foo 'mar) (foo 'tar)) > > (newline) > > (display "Choose 3: should be mar:") > > (Choose 3 (foo 'bar) (foo 'war 'har) (foo 'mar) (foo 'tar)) > > (newline) > > (display "Choose 4: should be tar:") > > (Choose 4 (foo 'bar) (foo 'war 'har) (foo 'mar) (foo 'tar)) > > (newline) > > (display "Choose 5: should be #f:") > > (Choose 5 (foo 'bar) (foo 'war 'har) (foo 'mar) (foo 'tar)) > > (newline) > > > > > > Best wishes, > > Arne > > -- > > Unpolitisch sein > > heißt politisch sein > > ohne es zu merken > > > > Attachments: > > * signature.asc > >
