QRegularExpression Problem

[cataylor559]

I am trying a simple pattern to extract numbers from a ASCII text file. The code I am using

QTextStream in( &file );
QString line = in.readline();
QRegularExpression re;
re.setPattern ( " -?[0-9]+\.?[0-9]* ");
line.section(re, 0);

a testing line was:
"Expected Vibration Frequency = 2.52 MHz"

Using RegexBuddy I tested the pattern and the results were
2.52.

However, when I implement the above code I get
2.52 Mhz

I tried the Qt expression of -?\d*\.?\d* and got the same thing. Why are the ascii characters after the digits included?

[koahnig]

welcome to devnet

My guess is that the syntax handling used is different. You need to check the documentation of "QRegularExpression":http://qt-project.org/doc/qt-5/qregularexpression.html

I have never used it. It has been implemented for Qt5. The older version "QRegExp":http://qt-project.org/doc/qt-5/QRegExp.html is also still available.There you have different possibilities.

The "example code for QRegExp":http://qt-project.org/doc/qt-5/qtwidgets-tools-regexp-example.html is a handy tool to check different possibilities. Unfortunately, it is still based on the older QRegExp.

[SGaist]

Hi and welcome to devnet,

I'd say you are using the wrong tool:

@
QString line("Expected Vibration Frequency = 2.52 MHz");
QRegularExpression re;
re.setPattern ( "-?[0-9]+\.?[0-9]*");
QRegularExpressionMatch match = re.match(line);
qDebug() << match.captured();
@

And you'll get 2.52

Hope it helps

[cataylor559]

Thanks for the help. I had not tried to use the QRegularExpressionMatch. Changing code as your example showed solved the problem.

Best,