Regex - does "or" require creating groups?

Asked Apr 08 '19 at 21:33

Active Apr 08 '19 at 21:33

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I use boost regex. I have created the following regex witch matches numbers from range [10-31]:

[1-2][0-9]|3[0-1]

I want to use that regex with additional matching for example:

<tag-[[1-2][0-9]|3[0-1]]>

but it doesn't work. It works when I create group:

<tag-([1-2][0-9]|3[0-1])>

For string <tag-22> I get two groups: <tag-22>, 22

Is it possible to create such regex without using groups ?

asked Apr 08 '19 at 21:33

Irbis

1

Use `` – Wiktor Stribiżew Apr 08 '19 at 21:35
Is it the only way ? Could you explain way using additional [ ] doesn't work ? – Irbis Apr 08 '19 at 21:36
What @WiktorStribiżew is showing is called non-capturing parentheses -- used for conceptual grouping without creating ("capturing") a group. This is the correct way. – Jay Apr 08 '19 at 21:37
1

No, you may also use branch reset groups that are also non-capturing, ``, but that is not necessary. – Wiktor Stribiżew Apr 08 '19 at 21:38

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