Clojure Q&A - Recent questions tagged regexp

regular expression with Classes for Unicode scripts, blocks, categories and binary properties

Tue, 22 Apr 2025 15:39:14 +0000

In Clojure, the following expression works fine:

(re-matches #"\p{Lu}" "Á") ;; => "Á"

But in Clojurescript, it returns nil.

It is not that Javascript doesn't support that kind of Unicode classess, but you have to activate them explicitly, whether in Java, they are activated by default.

E.g. In Javascript, the following code returns true:

/\p{Lu}/u.test("Á") // => true

But if I omit the Unicode flag (/u) I get false:

/\p{Lu}/.test("Á") // => false

I think this is probably because Clojure Script doesn't activates the Unicode flag for us.

If that the case, I think consistency between Clojurescript and Clojure could benefit a lot if the flag is activated by default.

What are the differences between JS and CLJS regular expressions?

Thu, 04 Jun 2020 09:56:34 +0000

I have this valid JavaScript regular expression:

/((([A-Za-z]{3,9}:(?:\/\/)?)(?:[\-;:&=\+\$,\w]+@)?[A-Za-z0-9\.\-]+|(?:www\.|[\-;:&=\+\$,\w]+@)[A-Za-z0-9\.\-]+)((?:\/[\+~%\/\.\w\-_]*)?\??(?:[\-\+=&;%@\.\w_]*)#?(?:[\.\!\/\\\w]*))?)/

(matching URLs)

Turns out it's not a valid CLJS one. It errors with:

#object[SyntaxError SyntaxError: unterminated parenthetical]

changit it to:

(def re #"^((([A-Za-z]{3,9}:(?://)?)(?:[\-;:&=\+\$,\w]+@)?[A-Za-z0-9\.\-]+|(?:www\.|[\-;:&=\+\$,\w]+@)[A-Za-z0-9\.\-]+)((?:/[\+~%/\.\w\-_]*)?\??(?:[\-\+=&;%@\.\w_]*)#?(?:[\.\!/\\\w]*))?)$")

(notice unescaped /)

works.

Is it a CLJS bug?

regex equality

Sat, 07 Sep 2019 14:03:23 +0000

How to check regexp equality in nested structures?

(= #"." #".") ;; #=> false
(= [#"."] [#"."]) ;; #=> false
(= ["."] ["."]) ;; #=> true

I believe that a regexp is a value object.
So two regexp are equal if they equals literally.

Is it possible to update = function for regexp equality support?

Maybe like this:

(defprotocol IEquals
 (equals [a b]))

(extend-protocol IEquals
  Object
  (equals [a b] (.equals a b))
  
  Pattern
  (equals [a b]
    (and
      (instance? Pattern b)
      (= (str a) (str b)))

And clojure.lang.Util.equiv uses
IEquals#equals instead of Object#equals.
But I down know how to call protocol method from clojure.lang.Util.