variadic-templates

问题 Below is an example program where a 'Container' class needs to store a list of 'Items' via a base class pointer. Having started with C++11/14 the natural choice would be to use std::unique_ptr and variadic templates in the case I have. However being new I cannot fathom how to convert the variadic list into and initialiser list for the vector of unique_ptr in a manner that compiles. Help is greatly appreciated as I have failed to find anything online that helps me with this issue so far

问题 I'm trying to write sum function using variadic template. In the code I would write something like sum(1, 2., 3) and it will return most general type of the sum (in this case - double ). The problem is with characters. When I call it like sum("Hello", " ", "World!") template parameters are deduces as const char [7] for example, thus it won't compile. I found the way to specify last argument as std::string("World!") , but it's not pretty, is there any way to achieve automatic type deduction to

问题 Just for practice I'm trying to write a variadic template that inputs some values into vector. I wrote the following: template <class T> void add(vector<T> *v, T n){ v->push_back(n); } template <class T, class... T2> void add(vector<T> *v, T n, T2... rest){ v->push_back(n); add(v, rest...); } To test these I use the following: vector<int> vI; add(&vI, 10, 30, 25); for (int i = 0; i < vI.size(); i++) cout << vI[i] << endl; Everything works as expected, but I'm wondering if the second template

问题 I'm facing with an issue in defining a grammar with variadic templates. I started by defining some simple grammars contained into some struct (e.g. Latitude, Longitude) as follows: #include <boost/fusion/include/adapt_struct.hpp> #include <boost/spirit/include/qi.hpp> #include <boost/variant.hpp> #include <iostream> #include <string> using namespace boost::spirit; template <class Attribute> using command_rule = qi::rule<std::string::iterator, Attribute, ascii::space_type>; template <class

问题 Okay, this is a really difficult one. I want to be able to get the subset of a parameter pack by choosing the parameter types at a given set of valid indices and then use that parameter pack as the argument list of a function. IE: template <size_t... indices_t> void func(pack_subset<indices_t..., args_t...>); //incorrect syntax, //not sure how else to write this //args_t is predetermined, this //function is a static member of //a variadic class template //For a parameter pack <float, double>

问题 So I am creating a type of event handler and I am in the process of writing an "Event Listener Wrapper", if you will. The basic idea is this: When you want to subscribe to an event, you create a function that should be called when the event fires. <-- already have that done (kinda, I'll explain) You put this listener function into a wrapper to pass the function onto the dispatcher. The dispatcher gets an event, finds the wrapper for you listener, and calls the underlying function with the

问题 Using gcc 4.7.3, I get the following error prog.cpp: In function ‘int main()’: prog.cpp:27:63: error: ‘Erase >::Result’ has not been declared with this code: template <typename... List> struct TypeList { enum { Length = sizeof...(List) }; }; template <typename ToErase, typename... List> struct Erase; template <typename ToErase> struct Erase<ToErase, TypeList<>> { typedef TypeList<> Result; }; template <typename ToErase, typename... Head, typename... Tail> struct Erase<ToErase, TypeList<Head..

问题 I want to define a generic strong alias type, i.e. a type template<typename T, auto ID = 0> class StrongAlias { T value; }; such that for a type T a StrongAlias<T> can be used in exactly the same way as T , but StrongAlias<T, 0> and StrongAlias<T, 1> are different types that can not be implecitly converted to each other. In order to mimic a T as perfectly as possible, I would like my StrongAlias to have the same constructors as T . This means I would like to do something like the following:

问题 I have a movable (but not copyable) type with a variadic template constructor struct foo { std::string a,b,c; foo(foo const&)=delete; foo(foo&&)=default; template<typename...T> for(T&&...); }; and I want to add it into a map: template<typename...T> void add_foo(std::map<std::string,foo>&map, const char*name, T&&...args) { map.emplace(std::piecewise_construct, // how? perhaps like this? std::forward_as_tuple(name), // no: std::forward_as_tuple(args)); // error here } 回答1: std::forward_as_tuple

问题 I am writing a function in C++ with a variable number of arguments (and different types) in this way template<typename ...Ts> void myFunction(Ts ...args) { //create std::tuple to access and manipulate single elements of the pack auto myTuple = std::make_tuple(args...); //do stuff return; } What i would like to do, but I don't know how, is to push and pop elements from the tuple, in particular the first element... something like //remove the first element of the tuple thereby decreasing its