Issue #9116 has been updated by phluid61 (Matthew Kerwin).


=begin
I, too, looked up and read the documentation, a couple of times.

I understand that the difference only applies when a ((|limit|)) parameter is given, and so examples of the new API would be:

 'a.b.c'.rsplit('.')    #=> ["a", "b", "c"], same as #split
 'a.b.c'.rpslit('.', 2) #=> ["a.b", "c"]

I would want to clarify some of the other edge cases (from ((%String#split%))) before continuing:

* If ((|pattern|)) is a (({String})), then its contents are used as the delimiter when splitting ((%str%)). If ((|pattern|)) is a single space, ((|str|)) is split on whitespace, with leading whitespace and runs of contiguous whitespace characters ignored.

Would this have some right-handed equivalent in ((%#rsplit%))?  E.g. "...with trailing whitespace and runs..."?  Or would it remain the same as ((%#split%))?  Or some third option?

E.g.:
  ' x  y '.rsplit(' ')   #=> ["x", "y"], same as split?
  ' x  y '.split(' ',-1) #=> ["", "x", "y"] or ["x", "y", ""] or ..?

* If the ((|limit|)) parameter is omitted, trailing null fields are suppressed. If ((|limit|)) is a positive number, at most that number of fields will be returned (if ((|limit|)) is (({1})), the entire string is returned as the only entry in an array). If negative, there is no limit to the number of fields returned, and trailing null fields are not suppressed.

Similarly, would this become: "...leading null fields..." in both instances?

E.g.:
  '..x..'.rsplit('.')    #=> ["x", "", ""] or ["", "", "x"] or ..?
  '..x..'.rsplit('.',-1) #=> ["", "", "x", "", ""], same as #split?

Note that this would be another difference from ((%#split%)), which ((*doesn't*)) depend on the ((|limit|)) parameter.

Seems like a lot of work.  What is the demand for this feature?
=end
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Feature #9116: String#rsplit missing
https://bugs.ruby-lang.org/issues/9116#change-43014

Author: artagnon (Ramkumar Ramachandra)
Status: Open
Priority: Normal
Assignee: 
Category: lib
Target version: 


There's nothing corresponding to Python's rsplit(). A quick glance at rb_str_split_m() tells me that it should be pretty trivial to implement. Is there any specific reason it hasn't already been done?


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