Hello, if you are looking for record introspection capabilities, I would recommend looking into SRFI-99[1], which combines static structure definition and dynamic reflection APIs. You're example could look like this:
(import (chicken format) srfi-42 srfi-99) (define-record-type egg-info make-egg-info egg-info? name author desc) (define (print-record/fields r) (define rtd (record-rtd r)) (do-ec (: f (rtd-field-names rtd)) (format #t "~a: ~a~%" f ((rtd-accessor rtd f) r)))) (print-record/fields (make-egg-info "F-operator" "Kon Lovett" "Shift/Reset Control Operators")) Ciao, Thomas -- [1]: https://srfi.schemers.org/srfi-99/srfi-99.html Am Fr., 23. Juni 2023 um 10:03 Uhr schrieb Pan Xie <xie...@skyguard.com.cn>: > #+begin_quote > Perhaps if you can explain why you need to know if a symbol is bound or > unbound, we might be able to help you better achieve your goal. > #+end_quote > > > For example, if I want to do things shown in following codes, it is useful > to get the > interned symbols from their names and also get their bound procedures: > > (define-record egg-info > name author desc) > > (define (show-egg-info egg) > (define (symbol-value sym) > (##sys#slot sym 0)) > > (define (getter field-name) > (symbol-value > (string->symbol > (format #f "egg-info-~a" > field-name)))) > > (let ((fields '(name author desc))) > (for-each > (lambda (f) > (format #t "~a: ~a~%" > f > ((getter f) egg))) > fields))) > > (show-egg-info (make-egg-info > "F-operator" > "Kon Lovett" > "Shift/Reset Control Operators")) > > I think it is a very common idiom in languages from Lisp family. So it is > important to know > how to check symbol is bound and get its value. Every scheme > implementation means for > business seriously should have the ability. > > Thanks > Pan > > > On 6/23/23 15:40, Peter Bex wrote: > > On Fri, Jun 23, 2023 at 03:32:38PM +0800, Pan wrote: > >> Ah, that make sense. It seems I can just use the '##sys#slot' procedure > to > >> accomplish all that tasks. > > Please don't use ##sys#slot unless you know what you're doing - the > > procedure is unsafe and will cause segmentation faults when used on > > non-block objects. Anything that starts with ##sys# or ##core# etc > > is intentionally undocumented because it's not meant for user code. > > > >> Would you please elaborate about the "transformed > >> name"? I see there are codes reference symbols like "##sys#slot" or > >> "scheme#list", but I can't find document describe them. Is there any > >> document I can look into? More specifically, how can I transfer "list" > to > >> "scheme#list"? Is there procedure can do that? > > scheme#list is the fully qualified symbol that means it's the "list" > > procedure from the "scheme" module. If you do "(import scheme)" and then > > just use "list" without prefix, it will get rewritten under the hood. > > > > Again, this is an implementation detail and not meant to be used > > directly. > > > > Perhaps if you can explain why you need to know if a symbol is bound or > > unbound, we might be able to help you better achieve your goal. > > > > Cheers, > > Peter > >
