Boost Spirit parser rule to parse square brackets

Question

I have to parse a string that can optionally have square brackets in it. For e.g. This can be my token string:

xyz[aa:bb]:blah

I have used rules like

• +(~qi::char_("\r\n;,="))
• +(~qi::char_("\r\n;,=") | "[" | "]")
• +(qi::char_ - qi::char_("\r\n;,="))

But none of them accepts the square brackets. Is there some special handling of [] in the parser?

Answer 1

You need to show the code. Here's a simple tester that shows that all of the parsers succeed and give the expected result:

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#include <boost/spirit/include/qi.hpp>
#include <iomanip>

namespace qi = boost::spirit::qi;

int main()
{
    using It = std::string::const_iterator;

    for(std::string const input : {"xyz[aa:bb]:blah"})
    {
        qi::rule<It, std::string()> rules[] = {
            +(~qi::char_("\r\n;,=")),
            +(~qi::char_("\r\n;,=") | "[" | "]"),
            +(qi::char_ - qi::char_("\r\n;,=")),
        };
        for(auto const& r : rules)
        {
            std::string out;
            std::cout << std::boolalpha
                      << qi::parse(begin(input), end(input), r, out) << " -> "
                      << std::quoted(out) << "\n";
        }
    }
}

Printing:

true -> "xyz[aa:bb]:blah"
true -> "xyz[aa:bb]:blah"
true -> "xyz[aa:bb]:blah"

The best guesses I have, not seeing your actual code:

• you are using a skipper that eats some of your characters (see Boost spirit skipper issues)

• you are using an input iterator that interferes

• you're invoking UB. To be honest, without context, this seems the most likely

If you show more code I'll happily diagnose which it is.