const std :: map< boost :: tuples :: tuple，std :: string&gt ;? [英] const std::map<boost::tuples::tuple, std::string>?

问题描述

// BOOST Includes
#include <boost/assign.hpp> 			// Boost::Assign
#include <boost/assign/list_of.hpp> 	// Boost::Assign::List_Of
#include <boost/assign/std/map.hpp> 	// Boost::Assign::Map_List_Of
#include <boost/tuple/tuple.hpp>    	// Boost::Tuples
// STD Includes
#include <map>
#include <vector>
#include <string>
// Using namespaces
using namespace std;
using namespace boost;
using namespace boost::assign;
// Consts
    const map<string, string> query_map = map_list_of<string, string>
    ("4556_SELECT_FILENAME", "SELECT FILENAME FROM Files WHERE PMU_ID = 4556")
    ("7552_SELECT_FILENAME", "SELECT FILENAME FROM Files WHERE PMU_ID = 7552")
    ("234x_SELECT_FILENAME", "SELECT FILENAME FROM Files WHERE PMU_ID = 2344 OR PMU_ID = 2345 OR PMU_ID = 2346 OR PMU_ID = 2347 OR PMU_ID = 2348")
    ("813x_SELECT_FILENAME", "SELECT FILENAME FROM Files WHERE PMU_ID = 8132 OR PMU_ID = 8133 OR PMU_ID = 8134 OR PMU_ID = 8135 OR PMU_ID = 8136");
    const map<string, std::vector<int>> vector_map = map_list_of<string, std::vector<int>>
    ("4556", list_of(4556))
    ("7552", list_of(7552))
    ("234x", list_of(2344)(2345)(2346)(2347)(2348))
    ("813x", list_of(8132)(8133)(8134)(8135)(8136));

使用boost - 可以使用init const std :: container进行测试等
一个const std :: map或std :: map很容易，如上面的代码所示。创建 const map< string，std :: vector< int>> 有点复杂，但仍然相当容易。

Using boost - it's possible to init const std::containers for testing etc. making a const std::map or std::map is pretty easy as the above code shows. Creating a const map<string, std::vector<int>> is a bit more complex - but still fairly easy.

我试图想出一个 const std :: map& boost :: tuples :: tuple< string，string，string> ;, string> 但我没有初始化它。有没有其他人有幸运吗？

I'm trying to come up with a const std::map<boost::tuples::tuple<string, string, string>, string> but I'm failing to initialize it. Has anyone else had any luck with it ?

// Typedefs
typedef boost::tuples::tuple<string, string, string> x3_string_tuple;
// Constants
const map<x3_string_tuple, string> query_selector_map = map_list_of<x3_string_tuple, string>
("4556", "SELECT", "FILENAME"), "4556_SELECT_FILENAME"); // ETC.

推荐答案

该映射需要是可比的（ std :: less ，因此需要定义一个运算符）。 boost :: tuple 的比较运算符在头文件 boost / tuple / tuple_comparison.hpp 中定义。

I tried this, and it fails because the keys of the map need to be comparable (with std::less, thus there needs to be an operator< defined). boost::tuple's comparison operators are defined in the header boost/tuple/tuple_comparison.hpp.

包含这些代码后，此代码工作正常：

Having included that, this code works fine:

#include <boost/assign/list_of.hpp>
#include <boost/tuple/tuple.hpp>
#include <boost/tuple/tuple_comparison.hpp>
#include <map>
#include <string>

using std::string;
typedef boost::tuple<string, string, string> tpl_t;

int main() {
    using boost::assign::map_list_of;
    std::map<tpl_t, string> const m = 
        map_list_of(tpl_t("a","b","c"), "c")(tpl_t("x","y","c"), "z");
}

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