Regex to repeatedly capture group within a larger match?

Question

Context, syntax highlighting in gedit.

Problem: I want to capture all occurrences within a specific area. Toy example:

other text here $5
keyword1 ->  (( ran$3dom$6t:,ext$9    ))
keyword1  -> ((    ran$2dom$4t:,ext$6 ))
other text here $7

I want to capture (highlight) al the $0-9 (single digit) occurrences, within the (( text )) of the keyword1. (here $3, $6, $9, $2, $4, $6 but NOT $5 and $7). This boils down to: How can I repeatedly capture a group within a larger match?

I can grab all the text where the groups can occur with: (?<=keyword1)|\(\(.*\)\) (gedit uses \g by default)

<context id="keyword1" style-ref="argument">
  <match>(?<=keyword1)|\(\(.*\)\)</match>
</context>

I have found this related question: How can I write a regex to repeatedly capture group within a larger match? but that answer uses infinite repetition inside look-behind which is, unfortunately, not supported by gedit (as far as i know). Any suggestion?

Answer 1

Description

To ensure you're only working on lines starting with your keyword, then I see this as a two step operation.

1. collect each of the lines you're interested
2. extract the $[0-9] substrings

Step 1

This regular expression captures lines that resemble keyword1 -> ((...))

keyword1\s*->\s*\(\(.*\)\)

Step 2

\$[0-9](?![0-9])(?=(?:(?!\(\().)*\)\))

This regular expression will do the following:

• find all dollar signs followed by a single digit that exist inside the ((...))

Example

Live Demo

https://regex101.com/r/wY3jM6/1

Sample text

other text here $5
keyword1 ->  (( ran$3dom$6t:,ext$9    ))
keyword1  -> ((    ran$2dom$4t:,ext$6 ))
other text here $7

Sample Matches

$3
$6
$9
$2
$4
$6

Explanation

NODE                     EXPLANATION
----------------------------------------------------------------------
  \$                       '$'
----------------------------------------------------------------------
  [0-9]                    any character of: '0' to '9'
----------------------------------------------------------------------
  (?!                      look ahead to see if there is not:
----------------------------------------------------------------------
    [0-9]                    any character of: '0' to '9'
----------------------------------------------------------------------
  )                        end of look-ahead
----------------------------------------------------------------------
  (?=                      look ahead to see if there is:
----------------------------------------------------------------------
    (?:                      group, but do not capture (0 or more
                             times (matching the most amount
                             possible)):
----------------------------------------------------------------------
      (?!                      look ahead to see if there is not:
----------------------------------------------------------------------
        \(                       '('
----------------------------------------------------------------------
        \(                       '('
----------------------------------------------------------------------
      )                        end of look-ahead
----------------------------------------------------------------------
      .                        any character
----------------------------------------------------------------------
    )*                       end of grouping
----------------------------------------------------------------------
    \)                       ')'
----------------------------------------------------------------------
    \)                       ')'
----------------------------------------------------------------------
  )                        end of look-ahead
----------------------------------------------------------------------