In the context of the regex dialect of XSLT 2.0, I am looking for two "meta-regexes" that analyse other regexes. Each is discussed in a part of its own. (Part 1 posted as: Meta-regex for variable-length matching regexes (XSLT)) Part 2 Aim: A regex that provides for pre-calculating the length of the match that a fixed-length matching ...

In the context of the regex dialect of XSLT 2.0, I am looking for two "meta-regexes" that analyse other regexes. Each is discussed in a part of its own. (Part 2 posted as: Meta-regex to find fixed length of regex match (XSLT)) Part 1 Aim: A regex that would identify all those regexes that might yield matches of varying length, as ...

hi i have this javascript regular expression for testing emails ^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$ the problem is that the email  should be optional so the regular expression should match: nothing or  ^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$