I want to expand a pack of variadic parameters into a struct member in C 11. My approach is the following:
template <typename... Ts>
struct cxpr_struct
{
constexpr cxpr_struct(Ts... Args) : t_(Args...) {}
std::array<int, sizeof...(Ts)> t_;
};
int main()
{
cxpr_struct(10, 20, 30);
}
However, this yields the following error:
<source>:208:16: error: missing template arguments before '(' token
208 | cxpr_struct(10, 20, 30);
|
I know that my code has flaws. E.g. the type of array is not determined from Ts (how can I do that?). But how would I do this the proper way? Is template argument deduction really not possible for the compiler?
EDIT: I have to use C 11
CodePudding user response:
due to c 11, you have to use something like that:
template <typename... Ts>
struct cxpr_struct
{
constexpr cxpr_struct(Ts... args) : t_{args...} {}
std::array<int, sizeof...(Ts)> t_;
};
template<typename... Ts>
cxpr_struct<Ts...> build(Ts...args){
return cxpr_struct<Ts...>(args...);
}
int main()
{
auto obj = build(10, 20, 30);
}
or better:
template <unsigned Size>
struct cxpr_struct
{
template<typename... Ts>
constexpr cxpr_struct(Ts... args) : t_{args...} {}
std::array<int, Size> t_;
};
template<typename... Ts>
cxpr_struct<sizeof...(Ts)> build(Ts...args){
return cxpr_struct<sizeof...(Ts)>(args...);
}
int main()
{
auto obj = build(10, 20, 30);
}