Problem with regular expression
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QRegExp exp("\b([a-gA-G][#bd]?)\b");
exp.setMinimal(true);
@This expression should match the seven musical notes in a insensitive manner. But it doesn't work because '#' is recognized as boundary character first the '[#bd]' character.
For example i tried it against 'C#' it match only the 'C' character like '#C#'.
I tried to not set Minimal and it doesn't work anyway, As I tried QRegExp::QRegExp2 and it doesn't work.
Is it a bug?
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'#' is non-word character and therefore matches it as a word boundary in 'C#'. It matches 'C#' without the word boundaries.
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QRegExp exp("([a-gA-G][#bd]?)")
@Why are you using word boundaries?
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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.
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My exp has to catch A# or C# only if they are "isolated" from the rest of the content page.
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so you could define whitespaces before / after:
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QRegExp exp("(\s[a-gA-G][#bd]?\s)")
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Yes but so RegExp engine catches the spaces too, and in my application this is not good,
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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?
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Sorry it continues to catch the spaces at the boundary of expression.
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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:
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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();
}
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I'm using QRegExp with QTextDocument::find function and QTextCursor,
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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.
