Variadic Templates – Recursion – Initializer Lists.

[Kenshin]

Seems to me like the only way to write functions/classes taking
variadic templates is by recursion. Is that true? Can the below work,
for iteration?

template<class� T>
auto func(const T&� t){

std::initializer_list<?> ilist = {t�}; //what should go here <?>//
for(const auto& arg : ilist)
//use arg//
}

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[Sergey S.]

On Dec 9, 9:08 pm, Kenshin <kenshin.himura.sakab...@gmail.com> wrote:
> Seems to me like the only way to write functions/classes taking
> variadic templates is by recursion. Is that true? Can the below work,
> for iteration?
>

> template<classÂ… T>
> auto func(const T&Â… t){
>
> std::initializer_list<?> ilist = {tÂ…}; //what should go here <?>//

> for(const auto& arg : ilist)
> //use arg//
>
> }

No. Recusion is not only one way to deal with variadic templates.
There is at least three solutions for your example. First was
demonstrated here:
http://groups.google.com/group/comp.std.c++/msg/927ea19b5201a7fa

Another two solutions (samples):

// if you expect only integers
template<int... Nums>
int make_sum()
{
auto list = {Nums...};

int result = 0;
return std::accumulate(list.begin(), list.end(), result);
}

// If you expect variadic params list of any type compatible each
other. For example, numeric types.
template<typename... Nums>
double make_sum(Nums ... nums)
{
auto list = {(double)nums...};

double result = 0;
return std::accumulate(list.begin(), list.end(), result);
}

with following usage:
std::cout << make_sum<1, 2, 3, 4, 5, 6>() << std::endl; // first case
std::cout << make_sum(1, 2, 3, 4.234, 5, 6, 7.435, 8, 9, 10) <<
std::endl; // second case

---
Best regards,
Sergey

[Pavel Minaev]

On Dec 9, 3:14 pm, "Sergey S." <flex_fer...@artberg.ru> wrote:
> template<int... Nums>
> int make_sum()
> {
> auto list = {Nums...};

What would be the inferred type of "list" in this example?

[Sergey S.]

On Dec 15, 8:17 pm, Pavel Minaev <int...@gmail.com> wrote:
> On Dec 9, 3:14 pm, "Sergey S." <flex_fer...@artberg.ru> wrote:
>
> > template<int... Nums>
> > int make_sum()
> > {
> > auto list = {Nums...};
>
> What would be the inferred type of "list" in this example?

Inferred type of "list" in this example is std::initializer_list<int>,
I think.

----------
Best regards,
Sergey