From: "Eregon (Benoit Daloze) via ruby-core" <ruby-core@...>
Date: 2025-04-21T03:30:44+00:00
Subject: [ruby-core:121698] [Ruby Feature#3388] regexp support for start_with? and end_with?

Issue #3388 has been updated by Eregon (Benoit Daloze).


`end_with?(/regex/)` if it recreates a Regexp on every call would be extremely slow. Languages with such APIs have learned the hard way it's a mistake to expose such APIs creating a Regexp behind the scenes.

One thing that could work is to lazily create and cache inside a Regexp object a variant of it with \z for this purpose. But it would likely increase footprint.

----------------------------------------
Feature #3388: regexp support for start_with? and end_with?
https://bugs.ruby-lang.org/issues/3388#change-112750

* Author: trans (Thomas Sawyer)
* Status: Feedback
* Assignee: naruse (Yui NARUSE)
----------------------------------------
=begin
 ruby-1.9.2-head > "aBcdeFghIj".start_with?(/abc/i)
 => false 
 
 In my implementation of start_with? it is easy enough to utilize #index, which works fine:
 
   def start_with?(pattern)
     index(pattern) == 0
   end
 
 But #end_with? is more difficult, and I had to use regular expressions.
 
     def end_with?(suffix)
       suffix = Regexp.escape(suffix) if String===suffix
       /#{suffix}$/.match(self) ? true : false
     end
 
 However, we might get rid of the '? true : false' and return the MatchData, since that could be useful information.
=end


---Files--------------------------------
0001-string.c-rb_str_start_with-rb_str_end_with-allow-Reg.patch (4.08 KB)


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