From: leo@...
Date: 2016-10-23T02:48:34+00:00
Subject: [ruby-core:77721] [Ruby trunk Bug#12862] Regular Expression Named Group Matching does not work with #{} (Similar? to issue #2778)

Issue #12862 has been updated by Leo Amigud.


Matthew Kerwin wrote:
> Leo Amigud wrote:
> > 
> > Sorry, not sure what you mean.
> > 
> > As a matter of fact i can use regexp like:
> > 
> > irb(main):013:0> numbers = '\d+'
> > => "\\d+"
> > irb(main):014:0> /\$#{numbers}.\d+/ =~ "$3.67"
> > => 0
> > irb(main):015:0>
> > 
> > to match the string, but using #{numbers} inside the named group somehow does not work.
> > 
> > Is that the expected behaviour?
> > 
> > Leo
> 
> It's what Hans quoted and said:
> 
> "When named capture groups are used **with a literal regexp** *[i.e. not an interpolated regexp]* ... the captured text is also assigned to local variables ..."
> 
> `/(?<dollars>#{numbers})/` is interpolated, not literal.
> 
> If you want to use interpolation and named captures, you can still get there using #match:
> 
> ~~~
> irb(main):001:0> numbers = '\d+'
> => "\\d+"
> irb(main):002:0> md = /\$(?<dollars>(#{numbers})).(?<cents>\d+)/.match "$4.67"
> => #<MatchData "$4.67" dollars:"4" cents:"67">
> irb(main):003:0> md['dollars']
> => "4"
> irb(main):004:0> md['cents']
> => "67"
> ~~~
> 
> or:
> 
> ~~~
> irb(main):001:0> numbers = '\d+'
> => "\\d+"
> irb(main):002:0> /\$(?<dollars>(#{numbers})).(?<cents>\d+)/ =~ "$4.67"
> => 0
> irb(main):003:0> $~['dollars']
> => "4"
> irb(main):004:0> $~['cents']
> => "67"
> ~~~

Thank you for the explanation!

Leo 

----------------------------------------
Bug #12862: Regular Expression Named Group Matching does not work with #{} (Similar? to issue #2778)
https://bugs.ruby-lang.org/issues/12862#change-61003

* Author: Leo Amigud
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-linux]
* Backport: 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN
----------------------------------------
Loading development environment (Rails 4.2.5)
irb(main):001:0> /\$(?<dollars>\d+)\.(?<cents>\d+)/ =~ "$3.67"
=> 0
irb(main):002:0> dollars
=> "3"


BUT:
irb(main):001:0> numbers = '\d+'
=> "\\d+"
irb(main):002:0> /\$(?<dollars>#{numbers})\.(?<cents>\d+)/ =~ "$3.67"
=> 0
irb(main):003:0> dollars
NameError: undefined local variable or method `dollars' for main:Object



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