clojure.string/substring

[Pierre-Yves Ritschard]

Hi list,

Since string operations are making their way to clojure.string to ease writing code for both clojurescript and clojure, would you be open to a patch that would add substring, using a one and two argument arity?

This is a very common need, and while java.lang.String already has a substring method, clojure.string would benefit from it - it would additionaly allow for negative offsets, as commonly found in most high level languages.

If you're open to the idea, I'm happy to open a JIRA and propose a patch for it.

Cheers!

[Thomas Heller]

There already is a substring function in core, so you can just do (subs "123" 1 2).

cljs.core/subs (or clojure.core/subs)

([s start] [s start end])

  Returns the substring of s beginning at start inclusive, and ending

  at end (defaults to length of string), exclusive.

HTH,

/thomas

[Pierre-Yves Ritschard]

Can't believe I missed this for the past 6 years :-)
Would then a patch adding support for negative indices be considered
(for both clojure and clojurescript) ?

[Andy Fingerhut]

In the past, there have been multiple requests for negative indices in Clojure's core library, and they have all been declined.  This ticket [1] and the links in its comments, provide some background.  I am not the one to approve or disapprove enhancement requests, but unless there has been some significant change in thought here, it seems unlikely such a change would be considered.

If you want them, it is pretty easy to implement your own versions of subs and vec that accept negative args.

Andy

[1] http://dev.clojure.org/jira/browse/CLJ-1042

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[Erik Assum]

There is also

https://github.com/expez/superstring

Which may or may not contain what you're looking for. 

Erik. 

-- 

i farta

[Alex Miller]

There is already clojure.core/subs for this.

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[Alex Miller]

Sorry on the previous email, didn't realize there was more in the inbox I hadn't read yet. :) 

I think the primary reasons negative indices have been declined is that the host (java.lang.String) doesn't give us a hand in implementing it and that it raises the question of whether negative indices should be supported in other contexts (unlikely). I think there's also a possible disconnect in substring that is start/end based vs start/length based.

ClojureScript didn't exist back then, but I think the issue of portability between Clojure and ClojureScript with host-supported implementations is worth considering, however I'm not sure that's a strong enough argument there to overcome the prior ones.