Problem with regular expression

[baysmith]

'#' is non-word character and therefore matches it as a word boundary in 'C#'. It matches 'C#' without the word boundaries.

@
QRegExp exp("([a-gA-G][#bd]?)")
@

Why are you using word boundaries?

[willypuzzle]

I need to parse web page to find musical chords and '#' is usually used to denote sharp (or diesis) note.
for example C# is a common sign I can found.

[willypuzzle]

My exp has to catch A# or C# only if they are "isolated" from the rest of the content page.

[giesbert]

so you could define whitespaces before / after:

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QRegExp exp("(\s[a-gA-G][#bd]?\s)")
@

[willypuzzle]

Yes but so RegExp engine catches the spaces too, and in my application this is not good,

[giesbert]

Come on, be a bit creative:

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QRegExp exp("\s([a-gA-G][#bd]?)\s")
@

moving the breakets would do it, right?

[willypuzzle]

Sorry it continues to catch the spaces at the boundary of expression.

[goetz]

You don't want the matched text, but the captions. Have a look at "QRegExp::cap() ":http://doc.qt.nokia.com/latest/qregexp.html#cap and the sample usage in the "Capturing Text":http://doc.qt.nokia.com/latest/qregexp.html#capturing-text seciton of the docs:

@
QRegExp exp("\s([a-gA-G][#bd]?)\s");
QString test("You like the chord C# very well!");
int pos = 0;
while((pos = exp.indexIn(test, pos)) != -1) {
qDebug() << "found '" + exp.cap(1) + "'";
pos += exp.matchedLength();
}
@

[willypuzzle]

I'm using QRegExp with QTextDocument::find function and QTextCursor,

[goetz]

I doubt that this will be possible with regular expressions (you can non-match the word boundary with a "positive lookahead assertion":http://doc.qt.nokia.com/latest/qregexp.html#assertions, but unfortunately there is no similar "look back" assertion. There is an jira issue open with a suggestion for this ("QTBUGS-2371":http://bugreports.qt.nokia.com/browse/QTBUG-2371), you can vote for it.