c++qt

What is the difference between QChar::isDigit() and QChar::isNumber()?

I read the documentation, it says for QChar::isNumber() that

Returns true if the character is a number (Number_* categories, not just 0-9);

However, when I click on the Number_*, it sends me to a http://qt-project.org/doc/qt-5/stylesheet-reference.html#number, which is about Style Sheets, and it doesn't make sense - what do Style Sheets have to do with QChar?

So to know the difference, I need to know what those Number_* categories really are, and I think the link in the documentation doesn't explain it, instead it points me to documentation about Style Sheets.

Solution

  • The (correct) hint is hidden in the documentation isDigit():

    Returns true if the character is a decimal digit (Number_DecimalDigit); otherwise returns false.

    Here, the Number_* link is correct:

    QChar::Number_DecimalDigit    3   Unicode class name Nd
QChar::Number_Letter          4   Unicode class name Nl
QChar::Number_Other           5   Unicode class name No

    So isNumber() will check if the given QChar is part of the unicode classes Nd, Nl or No. For example, ㊱ is classified as "Number, other", whereas Ⅱ (Roman numeral two) is classified as "Number, letter".