Question

Please help me with the regular expression itself. I am learning it. I don’t need replacement code.

I am working on wxWidget 2.8.12 with VS2008 (C++). I’d like to check whether TEST_STRING is float number. (-0.1, 0.1, 1 etc.). I think the expression itself is correct, I checked by tools. Do I make mistake with wxWidget?

wxString tmpStr = TEST_STRING;
wxRegEx reNegativeFloatNum(_("^[-]?[0-9]*\\.?[0-9]+$"));
bool tmp = reNegativeFloatNum.Compile(tmpStr);
     tmp = tmp && reNegativeFloatNum.IsValid();
if ( tmp && reNegativeFloatNum.Matches(tmpStr))
{
    //Do something
}
else
{
    //Do something else
}

My real question is why the regular expression doesn’t work? If I input ‘a’-‘Z’, the Matches() return ‘true’. Any one know? I just want to learn the regular expression.

Answer 1

As the OP really wants to use regexes, I looked at it in details and the original regex works just fine to me. Notice that you don’t need to use _() around regex string as this is not something you’d ever need to translate (_ is a short synonym for wxTRANSLATE()) and that Compile() is already called by the ctor. So here is a shorter version:

#include <wx/init.h>
#include <wx/regex.h>

int main(int argc, char **argv)
{
    wxInitializer init;
    if ( !init.IsOk() ) {
        puts("Failed to initialize wxWidgets.");
        return 1;
    }

    wxRegEx re("^[-]?[0-9]*\\.?[0-9]+$");
    return re.Matches(argv[1]);
}

And it works as expected:

    % ./a.out 123 || echo matches
    matches
    % ./a.out a-Z || echo matches
    <<<nothing>>>