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Is it possible to transform the types of a parameter pack and pass it on?
E.g. given the following:
template<class... Args> struct X {};
template<class T> struct make_pointer { typedef T* type; };
template<class T> struct make_pointer<T*> { typedef T* type; };
Can we define a template magic or something similar so that the following assertion holds:
typedef magic<X, make_pointer, int, char>::type A;
typedef X<int*, char*> B;
static_assert(is_same<A, B>::value, ":(");
901
Parameter packs (C++11) A parameter pack can be a type of parameter for templates. Unlike previous parameters, which can only bind to a single argument, a parameter pack can pack multiple parameters into a single parameter by placing an ellipsis to the left of the parameter name.
Variadic templates are class or function templates, that can take any variable(zero or more) number of arguments. In C++, templates can have a fixed number of parameters only that have to be specified at the time of declaration. However, variadic templates help to overcome this issue.
Pack expansion A pattern followed by an ellipsis, in which the name of at least one parameter pack appears at least once, is expanded into zero or more comma-separated instantiations of the pattern, where the name of the parameter pack is replaced by each of the elements from the pack, in order. template<class...
Yes we can do that
template<template<typename...> class List,
template<typename> class Mod,
typename ...Args>
struct magic {
typedef List<typename Mod<Args>::type...> type;
};
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