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Qt-interest Archive, March 2002
Fwd: QRegExp captured text

• Subject: Fwd: QRegExp captured text
• From: Bob Stafford <qtuser@xxxxxxxxxxxx>
• Date: Fri, 29 Mar 2002 13:31:21 -0600
• To: qt-interest@xxxxxxxxxxxxx

I've already posted this to qt-bugs, but since I've had no response yet I 
thought I'd try qt-interest. If someone at Trolltech is looking, please be 
aware that I've posted to both addresses, since it caused some problem last 
time I posted to both lists.

I've got  some more questions concerning Regular Expressions and captured
text.

The following test program

#include <qregexp.h>
#include <qstring.h>

int main(int argc,char *argv)
{
        QRegExp rx("comm ((:?-\\w\\s*)*) (param)");

        qDebug(QString("search=%1").arg(rx.search("comm -a -b -c param")));
        qDebug(QString("matchedLength=%1").arg(rx.matchedLength()));

        for(int i=0;i<10;i++)
        {
                qDebug(QString("cap(%1)=\"%2\"").arg(i).arg(rx.cap(i)));
        }
}

produces the following output

search=0
matchedLength=19
cap(0)="comm -a -b -c param"
cap(1)="-a -b -c"
cap(2)="-c"
cap(3)="param"
cap(4)=""
cap(5)=""
cap(6)=""
cap(7)=""
cap(8)=""
cap(9)=""


Given that the regular expression contains only two groups to be captured
((:?-\\w\\s*)*) and (param) I would expect list of captured strings to
contain three entries. The complete matched text (comm -a -b -c param), the
text caputered by the first grouping (-a -b -c) and the text captured by the
second group (param). As you can see cap(2) returns -c which I did not
expect, is this a bug or am I still mis-understanding the workings of the
text capture.

I'm using Qt 3.0.3

Thanks

Bob Stafford

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