template <typename Iterator>
struct parse_grammar
: qi::grammar<Iterator, std::string()>
{
parse_grammar()
: parse_grammar::base_type(start_p, "start_p"){
a_p = ',' > qi::double_;
b_p = *a_p;
start_p = qi::double_ > b_p >> qi::eoi;
}
qi::rule<Iterator, std::string()> a_p;
qi::rule<Iterator, std::string()> b_p;
qi::rule<Iterator, std::string()> start_p;
};
// implementation
std::vector<double> parse(std::istream& input, const std::string& filename)
{
// iterate over stream input
typedef std::istreambuf_iterator<char> base_iterator_type;
base_iterator_type in_begin(input);
// convert input iterator to forward iterator, usable by spirit parser
typedef boost::spirit::multi_pass<base_iterator_type> forward_iterator_type;
forward_iterator_type fwd_begin = boost::spirit::make_default_multi_pass(in_begin);
forward_iterator_type fwd_end;
// prepare output
std::vector<double> output;
// wrap forward iterator with position iterator, to record the position
typedef classic::position_iterator2<forward_iterator_type> pos_iterator_type;
pos_iterator_type position_begin(fwd_begin, fwd_end, filename);
pos_iterator_type position_end;
parse_grammar<pos_iterator_type> gram;
// parse
try
{
qi::phrase_parse(
position_begin, position_end, // iterators over input
gram, // recognize list of doubles
ascii::space); // comment skipper
}
catch(const qi::expectation_failure<pos_iterator_type>& e)
{
const classic::file_position_base<std::string>& pos = e.first.get_position();
std::stringstream msg;
msg <<
"parse error at file " << pos.file <<
" line " << pos.line << " column " << pos.column << std::endl <<
"'" << e.first.get_currentline() << "'" << std::endl <<
" " << "^- here";
throw std::runtime_error(msg.str());
}
// return result
return output;
}
我有以上示例代码（此处使用来自boost-spirit网站的代码）。
在规则a_p的语法中，我想使用语义动作并调用方法并将迭代器传递给它，如下所示：
a_p = ',' > qi::double_[boost::bind(&parse_grammar::doStuff(), this,
boost::ref(position_begin), boost::ref(position_end)];
如果方法doStuff的签名是这样的：
void doStuff(pos_iterator_type const& first, pos_iterator_type const& last);
任何想法如何做到这一点？ 我不介意任何方式（如果我可以使用boost :: phoenix或者不确定的方法），只要迭代器以其当前状态传递的方法。
答案 0 :(得分：3)
我不完全确定为什么你认为你'需要'你所描述的。我担心你的实际任务的解决方案可能很简单：
start_p = qi::double_ % ',' > qi::eoi;
然而，由于实际问题非常有趣，并且将位置交互器与istream_buf结合使用（而不仅仅是通常的（较慢的）boost::spirit::istream_iterator）具有它的优点，我将展示你如何用语义行为来做到这一点。
对于
的简单（但相当完整）测试主体int main()
{
std::istringstream iss(
"1, -3.4 ,3.1415926\n"
",+inF,-NaN ,\n"
"2,-.4,4.14e7\n");
data_t parsed = parse(iss, "<inline-test>");
std::cout << "Done, parsed " << parsed.size() << " values ("
<< "min: " << *std::min_element(parsed.begin(), parsed.end()) << ", "
<< "max: " << *std::max_element(parsed.begin(), parsed.end()) << ")\n";
}
带有语义操作的输出现在变为：
debug ('start_p') at <inline-test>:1:[1..2] '1' = 1
debug ('start_p') at <inline-test>:1:[4..8] '-3.4' = -3.4
debug ('start_p') at <inline-test>:1:[10..19] '3.1415926' = 3.14159
debug ('start_p') at <inline-test>:2:[2..6] '+inF' = inf
debug ('start_p') at <inline-test>:2:[7..11] '-NaN' = -nan
debug ('start_p') at <inline-test>:3:[1..2] '2' = 2
debug ('start_p') at <inline-test>:3:[3..6] '-.4' = -0.4
debug ('start_p') at <inline-test>:3:[7..13] '4.14e7' = 4.14e+07
Done, parsed 8 values (min: -3.4, max: inf)
注意它是怎样的
qi::double_来解析原始输入，因为这是我所知道的唯一可以轻松处理所有情况的事情（请参阅测试数据和其他问题：{{3 }}）以下是供将来参考的完整代码：
#define BOOST_SPIRIT_USE_PHOENIX_V3
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>
#include <boost/spirit/include/support_multi_pass.hpp>
#include <boost/spirit/include/classic_position_iterator.hpp>
#include <boost/phoenix/function/adapt_function.hpp>
namespace qi = boost::spirit::qi;
namespace phx = boost::phoenix;
namespace classic = boost::spirit::classic;
namespace ascii = boost::spirit::ascii;
typedef std::vector<double> data_t;
///////// USING A FREE FUNCTION
//
template <typename Grammar, typename Range>
double doStuff_(Grammar &grammar, Range pos_range)
{
// for efficiency, cache adhoc grammar:
static const qi::rule <typename Range::iterator, double()> r_double = qi::double_;
static const qi::grammar<typename Range::iterator, double()> g_double(r_double); // caching just the rule may be enough, actually
double value = 0;
qi::parse(pos_range.begin(), pos_range.end(), g_double, value);
std::cout << "debug ('" << grammar.name() << "') at "
<< pos_range.begin().get_position().file << ":"
<< pos_range.begin().get_position().line << ":["
<< pos_range.begin().get_position().column << ".."
<< pos_range.end ().get_position().column << "]\t"
<< "'" << std::string(pos_range.begin(),pos_range.end()) << "'\t = "
<< value
<< '\n';
return value;
}
BOOST_PHOENIX_ADAPT_FUNCTION(double, doStuff, doStuff_, 2)
template <typename Iterator, typename Skipper>
struct parse_grammar : qi::grammar<Iterator, data_t(), Skipper>
{
parse_grammar()
: parse_grammar::base_type(start_p, "start_p")
{
using qi::raw;
using qi::double_;
using qi::_1;
using qi::_val;
using qi::eoi;
using phx::push_back;
value_p = raw [ double_ ] [ _val = doStuff(phx::ref(*this), _1) ];
start_p = value_p % ',' > eoi;
// // To use without the semantic action (more efficient):
// start_p = double_ % ',' >> eoi;
}
qi::rule<Iterator, data_t::value_type(), Skipper> value_p;
qi::rule<Iterator, data_t(), Skipper> start_p;
};
// implementation
data_t parse(std::istream& input, const std::string& filename)
{
// iterate over stream input
typedef std::istreambuf_iterator<char> base_iterator_type;
base_iterator_type in_begin(input);
// convert input iterator to forward iterator, usable by spirit parser
typedef boost::spirit::multi_pass<base_iterator_type> forward_iterator_type;
forward_iterator_type fwd_begin = boost::spirit::make_default_multi_pass(in_begin);
forward_iterator_type fwd_end;
// wrap forward iterator with position iterator, to record the position
typedef classic::position_iterator2<forward_iterator_type> pos_iterator_type;
pos_iterator_type position_begin(fwd_begin, fwd_end, filename);
pos_iterator_type position_end;
parse_grammar<pos_iterator_type, ascii::space_type> gram;
data_t output;
// parse
try
{
if (!qi::phrase_parse(
position_begin, position_end, // iterators over input
gram, // recognize list of doubles
ascii::space, // comment skipper
output) // <-- attribute reference
)
{
std::cerr << "Parse failed at "
<< position_begin.get_position().file << ":"
<< position_begin.get_position().line << ":"
<< position_begin.get_position().column << "\n";
}
}
catch(const qi::expectation_failure<pos_iterator_type>& e)
{
const classic::file_position_base<std::string>& pos = e.first.get_position();
std::stringstream msg;
msg << "parse error at file " << pos.file
<< " line " << pos.line
<< " column " << pos.column
<< "\n\t'" << e.first.get_currentline()
<< "'\n\t " << std::string(pos.column, ' ') << "^-- here";
throw std::runtime_error(msg.str());
}
return output;
}
int main()
{
std::istringstream iss(
"1, -3.4 ,3.1415926\n"
",+inF,-NaN ,\n"
"2,-.4,4.14e7\n");
data_t parsed = parse(iss, "<inline-test>");
std::cout << "Done, parsed " << parsed.size() << " values ("
<< "min: " << *std::min_element(parsed.begin(), parsed.end()) << ", "
<< "max: " << *std::max_element(parsed.begin(), parsed.end()) << ")\n";
}