...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
So far, we've been using the syntax:
double_ >> *(',' >> double_)
to parse a comma-delimited list of numbers. Such lists are common in parsing and Spirit provides a simpler shortcut for them. The expression above can be simplified to:
double_ % ','
read as: a list of doubles separated by ','
.
This sample, again a variation of our previous example, demonstrates just that:
template <typename Iterator> bool parse_numbers(Iterator first, Iterator last, std::vector<double>& v) { using qi::double_; using qi::phrase_parse; using qi::_1; using ascii::space; using phoenix::push_back; using phoenix::ref; bool r = phrase_parse(first, last, // Begin grammar ( double_[push_back(ref(v), _1)] % ',' ) , // End grammar space); if (first != last) // fail if we did not get a full match return false; return r; }
The full cpp file for this example can be found here: ../../example/qi/num_list3.cpp