Question

I’m no expert on Regex. I’m trying to create a regular expression that will match the exact same number of opening and closing braces, but I’m stumped on how to do it.

An example:

nothing: important, a b { c {{{ a another {{ nothing }} }}} }

or:

one { two {{ error, forgot ending brace }}

The problem is that I don’t know how many braces I’m going to get beforehand. In the first example, I need to get the text { c {{{ a another {{ nothing }} }}} }. In the second I need to get {{ error, forgot ending brace }}.

Is it even possible to create a matching rule that will do this? (I’m using Qt Regex engine).

Answer 1

This problem cannot be solved using regular grammar => it cannot be done by regular expression.

However – from Dirk Vollmar’s comment – certain regex engines have extended functionality, e.g. the .NET one, which is capable of matching brackets using so called “balanced group definitions”.