Replace nested double brace pair with single

Question

Any ideas how to replace:

..((....))..

With:

..(...)..

Be aware, it is not a straight up replace of "((" with "(". The expression must determine that the child brace pair being removed is contained directly with the parent pair, with no other content.

Bonus points if anyone can figure out how to function recursively, e.g. "(((...)))" to "(...)"

Bonus points if you tag your question with a language or a tool. — revo, Jun 25 '18 at 11:02
I'm looking at T-SQL right now, although the question is independent of that. — Phil B, Jun 25 '18 at 11:14
Recursive matches are very engine specific. Hence asking for a language. — revo, Jun 25 '18 at 11:17
Ok. Am viewing stuff in VSCode so I guess that means this one: https://docs.rs/regex/0.2.10/regex/ — Phil B, Jun 25 '18 at 11:23
Do you think you may have unbalanced parentheses or escaped ones? — revo, Jun 25 '18 at 11:53
Nope. Can assume the input has balanced bracing. Although it could still work without e.g. "(((..))" matches inner portion "((..))" — Phil B, Jun 25 '18 at 12:07

Aman Chhabra · Accepted Answer · 2018-06-25T11:14:14.817

1

You can use this:

([(]*)(?:\([^)]*\))([)]*)

You just need to replace groups with empty string if even first group size is equal to second group or else use the minimum one.

Test:

(ABC)
((ABC))
(((ABC)))
((ABC)a)

Match Information:

Match 1
Full match  0-5 `(ABC)`
Group 1.    0-0 ``
Group 2.    5-5 ``
--> Hence, no update required
Match 2
Full match  6-13    `((ABC))`
Group 1.    6-7 `(`
Group 2.    12-13   `)`
--> As Group 1 and Group 2 size is same, replace those values with '' resulting to '(ABC)
Match 3
Full match  14-23   `(((ABC)))`
Group 1.    14-16   `((`
Group 2.    21-23   `))`
--> Same in this case as well
Match 4
Full match  24-30   `((ABC)`
Group 1.    24-25   `(`
Group 2.    30-30   ``
--> As group 1 and group 2 are not of same size, reduce to the min one which is group 2 (size 0) and hence no update required leaving it to '((ABC)A)'

Demo

edited Jun 25 '18 at 11:14

answered Jun 25 '18 at 11:05

Aman Chhabra

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I am fed up guys. Anyone who down votes, can you please state the reason of downvote as well – Aman Chhabra Jun 25 '18 at 11:07
((ABC)a) is a false positive. I didn't vote it down btw. – Phil B Jun 25 '18 at 11:28
@PhilB For that I have asked to check the size of group 1 and group 2 should match – Aman Chhabra Jun 25 '18 at 11:41

Replace nested double brace pair with single

1 Answers1