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I've finally found references to both Visual Studio's regular expressions for Find and Replace, and .NET's regular expression package, and now out of morbid curiousity I want to know: why the difference!?
I'm sure there's a technical, historical, or usability reason, but it confused the bajeepers [sp? ;-) ] out of me at first.
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A regular expression (shortened as regex or regexp; sometimes referred to as rational expression) is a sequence of characters that specifies a search pattern in text. Usually such patterns are used by string-searching algorithms for "find" or "find and replace" operations on strings, or for input validation.
*1 , * is greedy - it will match all the way to the end, and then backtrack until it can match 1 , leaving you with 1010000000001 . . *? is non-greedy. * will match nothing, but then will try to match extra characters until it matches 1 , eventually matching 101 .
In . NET, regular expression patterns are defined by a special syntax or language, which is compatible with Perl 5 regular expressions and adds some additional features such as right-to-left matching. For more information, see Regular Expression Language - Quick Reference.
There are also two types of regular expressions: the "Basic" regular expression, and the "extended" regular expression. A few utilities like awk and egrep use the extended expression. Most use the "basic" regular expression. From now on, if I talk about a "regular expression," it describes a feature in both types.
I'd speculate that the VS regexes are designed to match code well, having defined lots of handy shortcuts like :w for an entire word, or :i for a C++ identifier, or :q for a quoted string.
They usually don't need to handle arbitrary data that you'd need lookaround assertions and stuff like that for. Or at least that was lower on the priorities list.
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