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This sample demonstrates a parser for a comma separated list of numbers and
using a semantic action to collect the numbers into a std::vector
.
template <typename Iterator> bool parse_numbers(Iterator first, Iterator last, std::vector<double>& v) { using x3::double_; using x3::phrase_parse; using x3::_attr; using ascii::space; auto push_back = [&](auto& ctx){ v.push_back(_attr(ctx)); }; bool r = phrase_parse(first, last, // Begin grammar ( double_[push_back] >> *(',' >> double_[push_back]) ) , // 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: num_list2.cpp
This, again, is the same parser as before. This time, instead of summing
up the numbers, we stuff them in a std::vector
.
[&](auto& ctx){ v.push_back(_attr(ctx)); }