Example

This section shows you how the named regular expression classes may be used, for example, to match standard mathematical expressions, like 2 + 3 * (7 - 9) or 2 + 3 * 8 - 11. First, we need to define a number of regular expression classes:

group
\((?$expr)\)

factor
\d+|(?$group)

term
(?$factor)( \* (?$factor)| / (?$factor))*

expr
(?$term)( \+ (?$term)| - (?$term))*

Now, if you execute the Find All command in regular expression mode and enter the

(?$expr)

as regular expression to search for, all mathematical expressions in the document get selected.