cl-bnf

A simple BNF.

(:char . #\a) matches the given char.

(:string . "abc") matches the given string.

(:and exp ...) all expressions must match.

(:or exp ...) returns the first expression that matches.

(:* . exp) collect all strings matches the expression, if any.

(:? . exp) optional match.

#'some-function execute the function with the current char. must return boolean.

and can also be written in a form of sequence rule-c := rule-a rule-b.

or can also be written using :/, for example: rule-c := rule-a :/ rule-b.

rules & grammars

You can define a single rule using define-rule

(cl-bnf:define-rule word (:* . #'alpha-char-p) :call #'stringify)

...or using the define-grammar

(cl-bnf:define-grammar (abc . parser)
   abc := #\a #\b #\c
   cba := "cba"
   abc-cba := abc :/ cba
   parser := abc-cba)

(abc "abc") ;; (#\a #\b #\c)
(abc "cba") ;; "cba"

transformations

• :call apply a function to the results using funcall.
• :apply apply a function to the results using apply.
• :tag return a cons like (cons TAG RESULTS).
• If none where specified, it return all matches.

License

This project is released under the MIT License.

See license.