Royally reified regular expressions
Regal provides a syntax for writing regular expressions using plain Clojure data: vectors, keywords, strings. This is known as Regal notation.
Once you have a Regal form you can either compile it to a regex pattern
(java.util.regex.Pattern or JavaScript RegExp), or you can use it to create
a Generator (see test.check) for
generating values that conform to the given pattern.
Regal is Clojure and ClojureScript compatible, and glosses over some of the
differences in Java and JavaScript regex syntax (like \A / \z vs ^ / $).
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(require '[lambdaisland.regal :as regal])
;; Regal expression, like Hiccup but for Regex
(def r [:cat
[:+ [:range \a \z]]
"="
[:+ [:not \=]]])
;; Match values...
(regal/regex r)
;;=> #"([a-z]+)=([^=]+)"
(re-matches (regal/regex r) "foo=bar")
;;=> ["foo=bar" "foo" "bar"]
;; ... And generate them
(regal/gen r)
;;=> #clojure.test.check.generators.Generator{...}
(regal/sample r)
;;=> ("t=�" "d=5Ë" "zja=·" "uatt=ß¾" "lqyk=É" "xkj=q\f��" "gxupw=æ" "pkadbgmc=¯²" "f=Ã�J" "d=ç")- Strings and characters match literally. They are escaped, so
.matches a period, not any character,^matches a caret, etc. - A few keywords have special meaning. These are
:any(match any character, like.),:start(match the start of the input),:end(match the end of the input). - All other forms are vectors, with the first element being a keyword
[:cat forms...]: concatenation, match the given Regal expressions in order[:alt forms...]: alternatives, match one of the given options, like(foo|bar|baz)[:* form]: match the given form zero or more times[:+ form]: match the given form one or more times[:? form]: match the given form zero or one time[:range start end]: match a range of characters, like[a-z]. Takes one-character strings or characters.[:class entries...]: match any of the given characters or ranges, with ranges given as two element vectors. E.g.[:class [\a \z] [\A \Z] "_" "-"]is equivalent to[a-zA-Z_-][:not entries...]: like:class, but negates the result, equivalent to[^...][:repeat form min max]: repeat a form a number of times, like{2,5}
Copyright © 2020 Arne Brasseur
Licensed under the term of the Mozilla Public License 2.0, see LICENSE.