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Regular Expression: (?<=\D|^)(1[358]\d{9})(?=\D|$)

when I use boost regex:

char pat[] = {"(?<=\\D|^)(1[358]\\d{9})(?=\\D|$)"};
boost::regex reg(pat);

here throw an exception!

If I use POSIX, no exception, but can't match, for example:
boost::regex reg(pat, regbase::basic_syntax_group);
std::string str("+86 18601234567 tel.");

bool matched = regex_match(str, reg); // false!!!

who can tell me what's the matter? Pls send email to, thanks!

What I have tried:

when I use C#, it's ok.
for example:

string pat = @"(?<=\D|^)(1[358]\d{9})(?=\D|$)";
string myinfo= "custom name: name1;tel:+86 18601234567;addr:beijing.";
Regex rg = new Regex(pattern);
MatchCollection mc = rg.Matches(myinfo);
Updated 30-Apr-16 4:25am
PIEBALDconsult 17-Apr-16 13:04pm    
What is the Exception? Please use "Improve question" to add context and detail.
And don't put your email address in a public forum unless you enjoy spam.
Sergey Alexandrovich Kryukov 17-Apr-16 13:51pm    
The expression is shown; and the bug is obvious: '?'. I answered the question.
Sergey Alexandrovich Kryukov 17-Apr-16 13:57pm    
Thank you for your note; I removed my solution. The engine I tried did not understand '?'. I'll try another one, a very comprehensive ECMAScript's one...

Tried... It also doesn't work, reports "invalid group". Removing or escaping '?' makes it valid.

My conclusion would be: this feature is poorly supported by regex engines, should better be avoided. What do you think?

PIEBALDconsult 17-Apr-16 14:09pm    
My understanding is that .net has a lot of "extra" features that maybe should be avoided if one wants to support multiple engines, yes.
I don't know of an actual standard for RegEx.
Sergey Alexandrovich Kryukov 17-Apr-16 14:40pm    
That's right. Anyway, I tried Mozilla, Opera and Chrome. All show the same error related to '?'.
Note that these engines are very advanced; they support ECMAScript regular expressions, with Unicode and other advanced features.

1 solution

Sergey was close (?<=\D|^) is called a Positive Lookbehind assertion. It isn't supported in Posix and some versions of Java. C# supports both positive and negative lookbehind.

If you have to use Posix you will need to rework the expression to exclude the positive lookbehind. Nothing is broken it's a feature support issue.
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