How to write a boost::spirit::qi parser to parse an integer range from 0 to std::numeric_limits<int>::max()?

问题

I tried to use qi::uint_parser<int>(). But it is the same like qi::uint_. They all match integers range from 0 to std::numeric_limits<unsigned int>::max().

Is qi::uint_parser<int>() designed to be like this? What parser shall I use to match an integer range from 0 to std::numeric_limits<int>::max()? Thanks.

回答1:

Simplest demo, attaching a semantic action to do the range check:

uint_ [ _pass = (_1>=0 && _1<=std::numeric_limits<int>::max()) ];

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

template <typename It>
struct MyInt : boost::spirit::qi::grammar<It, int()> {
    MyInt() : MyInt::base_type(start) {
        using namespace boost::spirit::qi;
        start %= uint_ [ _pass = (_1>=0 && _1<=std::numeric_limits<int>::max()) ];
    }
  private:
    boost::spirit::qi::rule<It, int()> start;
};

template <typename Int>
void test(Int value, char const* logical) {
    MyInt<std::string::const_iterator> p;

    std::string const input = std::to_string(value);
    std::cout << " ---------------- Testing '" << input << "' (" << logical << ")\n";

    auto f = input.begin(), l = input.end();
    int parsed;
    if (parse(f, l, p, parsed)) {
        std::cout << "Parse success: " << parsed << "\n";
    } else {
        std::cout << "Parse failed\n";
    }

    if (f!=l) {
        std::cout << "Remaining unparsed: '" << std::string(f,l) << "'\n";
    }
}

int main() {
    unsigned maxint = std::numeric_limits<int>::max();

    MyInt<std::string::const_iterator> p;

    test(maxint  , "maxint");
    test(maxint-1, "maxint-1");
    test(maxint+1, "maxint+1");
    test(0       , "0");
    test(-1      , "-1");
}

Prints

 ---------------- Testing '2147483647' (maxint)
Parse success: 2147483647
 ---------------- Testing '2147483646' (maxint-1)
Parse success: 2147483646
 ---------------- Testing '2147483648' (maxint+1)
Parse failed
Remaining unparsed: '2147483648'
 ---------------- Testing '0' (0)
Parse success: 0
 ---------------- Testing '-1' (-1)
Parse failed
Remaining unparsed: '-1'

来源：https://stackoverflow.com/questions/40866528/how-to-write-a-boostspiritqi-parser-to-parse-an-integer-range-from-0-to-std