[SOLVED]Weird regex behavior...

wecing

Hi guys,

I have some problem with regex in Qt. I wrote a small program to match all consecutive numbers in a given string, but the program fails to work correctly.

Here is the code:
@#include <QtGui>
#include <iostream>

int main() {
QRegExp rx("[0-9]+");
QString str = "35.625(+2.125)";
int pos = 0;

 while ((pos = rx.indexIn(str, pos)) != -1) {
      std::cout << rx.cap(1).toStdString() << " ";
      pos += rx.matchedLength();
 }
 
 std::cout << std::endl;
 return 0;

}
@

And the output is... an empty line?????

wecing

Well... In fact I want to match all numbers; I added some redundant parenthesis, and "(([0-9]*)\.?([0-9]+))" works perfectly for me.

Why? According to the doc --
bq. For historical reasons, quantifiers (e.g. ) that apply to capturing parentheses are more "greedy" than other quantifiers. For example, a(a)* will match "aaa" with cap(1) == "aaa". This behavior is different from what other regexp engines do (notably, Perl). To obtain a more intuitive capturing behavior, specify QRegExp::RegExp2 to the QRegExp constructor or call setPatternSyntax(QRegExp::RegExp2).

Parenthesis may cause problems; but I did use QRegExp::RegExp2, but it didn't help.

lgeyer

You didn't specify any subexpressions (or capture groups or whatever you might call them) so the desired result is at rx.cap(0), not rx.cap(1).

@
...
std::cout << rx.cap(0).toStdString() << " ";
...

35 625 2 125
@

EDIT Looks like you've already solved your initial problem.

wecing

Ahh... Got it. Thanks.