3
這是來自a previous question的後續問題。製作來自齊靈的共享指針矢量
我可以從我的語法解析字符串的向量，但我似乎無法解析到共享指針字符串的向量;即std::vector<std::shared_ptr<std::string> >，並需要一些幫助。
我的編譯頭：
#define BOOST_SPIRIT_USE_PHOENIX_V3 1
#include <boost/spirit/include/qi_core.hpp>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix_core.hpp>
#include <boost/spirit/include/phoenix_operator.hpp>
#include <iostream>
#include <string>
#include <boost/spirit/include/phoenix_stl.hpp>
#include <boost/phoenix/bind/bind_member_function.hpp>
#include <boost/spirit/include/phoenix_fusion.hpp>
// this solution for lazy make shared comes from the SO forum, user sehe.
// https://stackoverflow.com/questions/21516201/how-to-create-boost-phoenix-make-shared
// post found using google search terms `phoenix construct shared_ptr`
// changed from boost::shared_ptr to std::shared_ptr
namespace {
template <typename T>
struct make_shared_f
{
template <typename... A> struct result
{ typedef std::shared_ptr<T> type; };
template <typename... A>
typename result<A...>::type operator()(A&&... a) const {
return std::make_shared<T>(std::forward<A>(a)...);
}
};
template <typename T>
using make_shared_ = boost::phoenix::function<make_shared_f<T> >;
}
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
template<typename Iterator, typename Skipper = ascii::space_type>
struct SystemParser : qi::grammar<Iterator, std::vector<std::shared_ptr<std::string> >(), Skipper>
{
SystemParser() : SystemParser::base_type(variable_group_)
{
namespace phx = boost::phoenix;
using qi::_1;
using qi::_val;
using qi::eps;
using qi::lit;
var_counter = 0;
declarative_symbols.add("variable_group",0);
variable_group_ = "variable_group" > genericvargp_ > ';';
genericvargp_ = new_variable_ % ','; //
new_variable_ = unencountered_symbol_ [_val = make_shared_<std::string>() (_1)];
unencountered_symbol_ = valid_variable_name_ - (encountered_variables | declarative_symbols);
valid_variable_name_ = +qi::alpha >> *(qi::alnum | qi::char_("[]_"));
// debug(variable_group_); debug(unencountered_symbol_); debug(new_variable_); debug(genericvargp_);
// BOOST_SPIRIT_DEBUG_NODES((variable_group_) (valid_variable_name_) (unencountered_symbol_) (new_variable_) (genericvargp_))
}
// rule declarations. these are member variables for the parser.
qi::rule<Iterator, std::vector<std::shared_ptr<std::string> >(), Skipper > variable_group_;
qi::rule<Iterator, std::vector<std::shared_ptr<std::string> >(), Skipper > genericvargp_;
qi::rule<Iterator, std::shared_ptr<std::string()> > new_variable_;
qi::rule<Iterator, std::string()> unencountered_symbol_;
qi::rule<Iterator, std::string()> valid_variable_name_;
unsigned var_counter;
qi::symbols<char,int> encountered_variables;
qi::symbols<char,int> declarative_symbols;
};
與驅動程序代碼：
int main(int argc, char** argv)
{
std::vector<std::shared_ptr<std::string> > V;
std::string str = "variable_group x, y, z; ";
std::string::const_iterator iter = str.begin();
std::string::const_iterator end = str.end();
SystemParser<std::string::const_iterator> S;
bool s = phrase_parse(iter, end, S, boost::spirit::ascii::space, V);
if (s)
{
std::cout << "Parse succeeded: " << V.size() << " variables\n";
for (auto& s : V)
std::cout << " - '" << s << "'\n";
}
else
std::cout << "Parse failed\n";
if (iter!=end)
std::cout << "Remaining unparsed: '" << std::string(iter, end) << "'\n";
return 0;
}
的內容是正確分析，但所得到的矢量的長度爲0，而它應該是長度3的不知何故，std::shared_ptr<string>沒有被推到由規則genericvargp_產生的向量的背面。
我已經嘗試了很多事情，包括讀取測試解析中的所有調試信息，以及規則定義的%=符號的位置，這些符號應該用於存在未分配的語義操作的規則_val除非我錯了。我也玩了一整天，用phx::bind手動推到_val的背面，但沒有任何地方。我進一步證實了sehe在另一個答案中提供的make_shared_對於std :: shared_ptr實際上是懶惰的。
順便說一句，我也努力與得到一個unencountered_symbol_的結果添加到encountered_variables以強制變量名稱的唯一...
的問題似乎是的結果的傳播new_variable_規則到genericvargp_規則中的共享指針的期望向量上。
我想補充一點，我故意留在氣的價值： ：符號。現在，它是int，但後來我將放入shared_ptr < Node >，以便在解析函數時，可以將找到的符號與適當的節點相關聯。所以留下整數對我來說很重要。 – ofloveandhate