From: "phluid61 (Matthew Kerwin)" <matthew@...>
Date: 2013-04-12T13:53:14+09:00
Subject: [ruby-core:54213] [ruby-trunk - Feature #8110] Regex methods not changing global variables


Issue #8110 has been updated by phluid61 (Matthew Kerwin).


=begin
sam.saffron (Sam Saffron) wrote:
 > sorry, I really did not mean to say the language should ship a crazy _G
 > macro it was just a simple polyfill in the app. even with the polyfill
 > it is way verbose.  
 > 
 > #app code not ruby
 > def _G(re)
 >   Regexp.new(re.to_s, re.options | defined?(Regexp::SKIP_GLOBALS) ?
 >         Regexp::SKIP_GLOBALS : 0)
 > end

Why not just do the following (evil, wicked, untenable) hack?

 class Regexp; SKIP_GLOBALS = 0 unless defined? SKIP_GLOBALS; end

You still can't use (({//})) or (({%r()})) literals, but it means you can use
 Regexp.new('foo|bar(baz)?', Regexp::SKIP_GLOBALS)
without fear.
=end

----------------------------------------
Feature #8110: Regex methods not changing global variables
https://bugs.ruby-lang.org/issues/8110#change-38485

Author: prijutme4ty (Ilya Vorontsov)
Status: Assigned
Priority: Normal
Assignee: matz (Yukihiro Matsumoto)
Category: core
Target version: next minor


It is useful to have methods allowing pattern matching without setting global variables. It can be very hard to understand where the problem is when you for example insert a string like `puts pat === my_str` and your program fails in a place which is far-far away from inserted place. This can happen due to replacing global variables of previous pattern match. I caught to this when placed pattern-match inside case-statement and shadowed global vars which were initially filled by match in when-statement.
For now one can extract pattern matching into another method thus defining method-scope for that variables. But sometimes it looks like an overkill. May be simple method like #match_globalsafe can prevent that kind of errors. At least when a programmer see such a method in a list of methods, he's warned that usual match can cause such problems.


-- 
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