Question

What’s the easiest way to parse a file with

[[1, 2, 3, 4], [8, 9, 10, 11], ...]

into a vector of QRectF (a struct with four floats)?

Answer 1

have you looked at boost’s spirit library? I think it’s an amazing library and if I recall correctly they have examples in the tutorial very similar to what you want.

EDIT: This puts you at about the right place: http://www.boost.org/doc/libs/release/libs/spirit/doc/html/spirit/qi/tutorials/warming_up.html

EDIT:
Sigh…I haven’t looked at c++ in over a year (and I haven’t looked at spirit in over 4 years) so this took about an hour to put together. Here’s the working example:

# include <boost/spirit/include/qi.hpp>
using boost::spirit::qi::int_;
using boost::spirit::qi::char_;
using boost::spirit::qi::lit;
using boost::spirit::ascii::space;
using boost::spirit::ascii::space_type;
using boost::spirit::qi::rule;
using boost::spirit::qi::phrase_parse;

#include <boost/fusion/include/adapt_struct.hpp>

#include <string>
using std::string;

#include <iostream>
using std::cout;
using std::endl;

#include <vector>
using std::vector;

struct holder {
    int n1;
    int n2;
    int n3;
    int n4;
};
BOOST_FUSION_ADAPT_STRUCT(::holder, (int,n1) (int,n2) (int, n3) (int, n4))

int main() {
    string s = "[[1,2,3,4], [4,3,2,1]]";
    vector<holder> v;

    // I admit it, I was wrong. It's 3 lines of parsing.
    rule<string::iterator, holder(), space_type> holder_p = 
        lit("[") >> int_ >> ',' >> int_ >> ',' >> int_ >> ',' >> int_ >> ']';
    rule<string::iterator, vector<holder>(), space_type > holder_list_p = 
        char('[') >> (holder_p % ',') >> ']';
    bool r = phrase_parse(s.begin(), s.end(), holder_list_p, space, v);

    if (r) {
        for (vector<holder>::const_iterator it = v.begin(); it != v.end(); it++) {
            cout << "n1: " << it->n1 << ", n2: " << it->n2 << 
                    ", n3: " << it->n3 << ", n4: " << it->n4 << endl;
        }
    }
    return 0;
}