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Diffstat (limited to 'src/corelib/text/qregularexpression.cpp')
| -rw-r--r-- | src/corelib/text/qregularexpression.cpp | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/src/corelib/text/qregularexpression.cpp b/src/corelib/text/qregularexpression.cpp index e05bef450b..9774dc0559 100644 --- a/src/corelib/text/qregularexpression.cpp +++ b/src/corelib/text/qregularexpression.cpp @@ -443,6 +443,38 @@ QT_BEGIN_NAMESPACE Other differences are outlined below. + \section2 Different pattern syntax + + Porting a regular expression from QRegExp to QRegularExpression may require + changes to the pattern itself. + + In certain scenarios, QRegExp was too lenient and accepted patterns that + are simply invalid when using QRegularExpression. These are somehow easy + to detect, because the QRegularExpression objects built with these patterns + are not valid (cf. isValid()). + + In other cases, a pattern ported from QRegExp to QRegularExpression may + silently change semantics. Therefore, it is necessary to review the + patterns used. The most notable cases of silent incompatibility are: + + \list + + \li Curly braces are needed in order to use a hexadecimal escape like + \c{\xHHHH} with more than 2 digits. A pattern like \c{\x2022} neeeds to + be ported to \c{\x{2022}}, or it will match a space (\c{0x20}) followed + by the string \c{"22"}. In general, it is highly recommended to always use + curly braces with the \c{\\x} escape, no matter the amount of digits + specified. + + \li A 0-to-n quantification like \c{{,n}} needs to be ported to c{{0,n}} to + preserve semantics. Otherwise, a pattern such as \c{\d{,3}} would + actually match a digit followed by the exact string \c{"{,3}"}. + + \li QRegExp by default does Unicode-aware matching, while + QRegularExpression requires a separate option; see below for more details. + + \endlist + \section2 Porting from QRegExp::exactMatch() QRegExp::exactMatch() in Qt 4 served two purposes: it exactly matched |