RegEx/RegularExpression/Group.regex.txt
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# Matches groups in a regular expression
(?<!\\)\( # An open parenthesis (?<HasOptions>\?)? # Any group options are preceeded by a ? (?(HasOptions)(?: # If we have options, figure out what they are: (?> # It can be only one: (?:\<(?<GroupName>\w+)\>) # a <GroupName> | (?<Atomic>\>) # An atomic expression atomic (>) | (?<NoCapture>\:) # A non capturing expression (:) | (?<LookBehind>\<\=) # A lookbehind (<=) | (?<NegativeLookBehind>\<\!) # A negative lookbehind (<!) | (?<LookAhead>\=) # A lookahead (=) | (?<NegativeLookAhead>\!) # A negative lookahead (!) | (?<If>\( # Last but not least, it can be an if, which is a nested expression (?> \\\( # an escaped open parenthesis OR | \\\) # an escaped close parenthesis OR | [^\(\)]+ # any number of non-parenthesis characters OR | \((?<Depth>) # an open parenthesis (in which case increment depth) OR | \)(?<-Depth>) # a closed parenthesis (in which case decrement depth) )*(?(Depth)(?!)) # and thus has to use a balancing expression to match until depth is 0 \) # don't forget the closing parenthesis! ) ) )) (?<Pattern> # Now we are in the pattern body. (?> # We just need to capture... \\\( # an escaped open parenthesis OR | \\\) # an escaped close parenthesis OR | [^\(\)]+ # any number of non-parenthesis characters OR | \((?<Depth>) # an open parenthesis (in which case increment depth) OR | \)(?<-Depth>) # a closed parenthesis (in which case decrement depth) )*(?(Depth)(?!)) # until depth is 0. )\) # then close out our <Pattern> group and and don't forget the closing parenthesis! |