Regular expression of Qt don't match as expected

Question

Why is the regular expression of Qt a little different? I can match correctly in regular matching software, but not in Qt. For example.

QString tstring = "scale(1.1) rotate(180) translate(1,0)";
QRegExp re("(?<=[\\)])."); 
QStringList tlist = tstring.split(re);

I want to separate the three with spaces to get the three QString "scale(1.1)", "rotate(180)" "translate(1,0)"

Maybe you want to use [`QRegularExpression`](https://doc.qt.io/qt-5/qregularexpression.html#details) which uses the Perl syntax. — m7913d, Jul 16 '20 at 09:49
With which matching software you matched any of these? All I can match with your pattern are the two whitespaces. Your RegExp says: Match one char following a ")" - are you sure, thats what you want? — derM - not here for BOT dreams, Jul 16 '20 at 09:49
I can also match two spaces with the online matching tool, but not in Qt. — sorrowfeng, Jul 16 '20 at 09:54
Except for those, some QString are like "matrix (3 1-1 3 30 40)" and cannot be divided directly by spaces. — sorrowfeng, Jul 16 '20 at 09:57

score 1 · Accepted Answer · answered Jul 16 '20 at 13:02

Different syntaxes of regular expressions exist. Qt implements some of them:

QRegularExpression (>= Qt5): implements Perl-compatible regular expressions
QRegExp: implements multiple regular expression forms, see QRegExp::PatternSyntax
- QRegExp::RegExp (the default): Qt's regexp language modeled on Perl's regexp language
- QRegExp::Wildcard: similar to wildcards used by shells.
- QRegExp::W3CXmlSchema11: implementation of the W3C XML Schema 1.1 specification.
- ...

Note that QRegularExpression is the recommended one:

The QRegularExpression class introduced in Qt 5 is a big improvement upon QRegExp, in terms of APIs offered, supported pattern syntax and speed of execution.

A detailed overview of the differences between QRegExp and QRegularExpression can be found in the docs.

Regular expression of Qt don't match as expected

1 Answers1