Macro in the keyword package about cl-bnf HOT 5 CLOSED

Yes, but also extending grammars, or importing rules from other grammars might be possible. It is quite similar to packages and symbols, but I'd tend not to try to map the former to the latter, because they operate on different semantic levels.

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@Harleqin Thanks for bring this up. I'm still thinking on a better (proper) way to write the rules. I'll do some work on the weekend to improve this. Any suggestions?

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The obvious solution that changes as little as possible is to actually name the macro cl-bnf:|:=|. You'd need to write (defmacro |:=| …) or (defmacro \:= …), and every invocation would need to be changed as well.

Going a bit further would be to rename it to defrule or define-rule. This would also make it clearer that it is a toplevel definition (I had to look twice at the documentation to understand this).

Thinking a bit more about it, as a user I'd maybe not want the rules to be global, but always part of a grammar, so that I can define several grammars in one program without name clashes. You can then maybe keep the :=, because it would be interpreted by a defgrammar macro, instead of being a macro itself.

(defgrammar json-number ()
  (:= decimal-number (:many (:one #'numeric-char-p)))
  (:= real-number (:or (:and #'decimal-number
                             (:char #\.)
                             #'decimal-number)
                       (:and #'decimal-number
                             (:char #\.))))
  (:= signed-part (:or (:char #\+) (:char #\-)))
  (:= exp-chars (:or (:char #\e)
                     (:char #\E)))
  (:= exp-part (:or (:and #'exp-chars
                          #'signed-part
                          #'decimal-number)
                    (:and #'exp-chars
                          #'decimal-number)))
  (:= numeric (:or #'real-number
                   #'decimal-number))
  (:= number-literal (:or (:and #'numeric
                                #'exp-part)
                          #'numeric)
      :call (lambda (matches)
              (cons :number (stringify matches))))

(parse json-number number-literal "1e3")

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Yeah, that's pretty much what I had in mind. See #5.

Perhaps, we can keep both...the defgrammar and defrule.

(defrule real-number 'the rule' :apply ...))
(defrule decimal-number 'the rule' :apply ...))

(defgrammar json-parser ()
  (number := (:or #'real-number #'decimal-number) :apply ...)
  (strings := 'rule' :apply ...)
  (...)
  (parse number strings objects array))

Maybe this way, we can allow sharing rules.

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Both macros are available now. Thanks for all the help and ideas.

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