When building patterns it is often helpful to group sub-patterns together, for example to use the group in alternation or to apply a quantifier. For example,
A group is created by wrapping the sub-pattern in \%(...). Technically, this creates a non-capturing group, which is slightly different from a capturing group which is discussed in the next section. All information in this section applies to both capturing and non-capturing groups, but this section uses the non-capturing notation because it is more efficient when capturing is not required.
| Notation | Group Type |
|---|---|
| \%( ... \) | Non-capturing |
| \( ... \) | Capturing |
As a simple example, suppose we want to construct a pattern that matches "abcabcabc". Following the discussion in the quantifiers section, we might write:
abc\{3\}
Let's test this pattern using the following buffer:
First we execute the search
then select the matching text
what happened? The quantifier is applied to the atom on the left, which in this case is "c".
To fix this, we need to create a group around the "abc" so that the entire string is treated as an atom:
\%(abc\)
then apply the quantifier to the group:
\%(abc\)\{3\}
and select the matched text
which confirms that the updated pattern achieves our goal.