How to obtain the types in a C++11 parameter pack?

Question

I'm not sure that I worded the question in the most effective way, but I'm just now starting to use C++11 and am having trouble applying its new features to the problem at hand. I have the following notional function: ``` template std::vector foo() ``` I would like `foo()` to return a `vector` that contains a `type_index` value for each of the types in the parameter pack `Args`. For example, `foo, double>()` would return a `vector` containing `{ type_index(typeid(int)), type_index(typeid(vector)), type_index(typeid(double)) }`. Notionally, I would like to iterate over the types in the pack and invoke the above transform on each of them (i.e. given a type `T`, return `type_index(typeid(T))`. I feel like there should be a clean way to accomplish this, but it's not clear to me how to operate the variadic template machinery to make this work. Is my intuition correct?

Accepted Answer

The simplest way to "iterate" over types in a pack is to use pack expansion to repeat the desired pattern. In this case you'd write something like the following:

```
return { type_index(typeid(Args))... }
```

How to obtain the types in a C++11 parameter pack?

Solution

Problem