3 ms·

Heh, thought it was from Lisp. No problem with scoping there.

• kazinator 6y ago
  with macros in Lisp tend to be sanely designed: they explicitly list the symbols that are to be introduced into the scope. I don't think I've never seen a "bring the whole set of the currently defined slots of this class/struct into this scope as locals". Oh, you can do it. his is the TXR Lisp interactive listener of TXR 249. Quit with :quit or Ctrl-D on an empty line. Ctrl-X ? for cheatsheet. Use full-strength TXR for tough tasks, or dilute with shell scripts. 1> (defmacro with (struct obj . body) (with-gensyms (obj-sym) ^(let ((,obj-sym ,obj)) (symacrolet ,(mapcar (op list @1 ^(qref ,obj-sym ,@1)) (slots struct)) ,*body)))) with 2> (with time (time-struct-utc (time)) (list year month day)) (2021 1 30) Expansion: 3> (macroexpand '(with time (time-struct-utc (time)) (list year month day))) (let ((#:g0016 (time-struct-utc (time)))) (symacrolet ((time-local #:g0016.time-local) (time-utc #:g0016.time-utc) (time-string #:g0016.time-string) (time-parse #:g0016.time-parse) (year #:g0016.year) (month #:g0016.month) (day #:g0016.day) (hour #:g0016.hour) (min #:g0016.min) (sec #:g0016.sec) (dst #:g0016.dst) (gmtoff #:g0016.gmtoff) (zone #:g0016.zone)) (list year month day))) Total expansion; symacrolet gone, a.b desugared into (slot a 'b): 4> (expand '(with time (time-struct-utc (time)) (list year month day))) (let ((#:g0017 (time-struct-utc (time)))) (list (slot #:g0017 'year) (slot #:g0017 'month) (slot #:g0017 'day)))