Non-type variadic function templates in C++11

Question

I saw a blog post which used non-type variadic templates (currently not supported by gcc, only by clang).

template 
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Answer 1

Here are two ways of defining a variadic function template only accepting int parameters. The first one generates a hard-error when instantiated, the second uses SFINAE:

template
struct and_: std::true_type {};

template
struct and_
: std::integral_constant<
    bool
    , First::value && and_::value
> {};

template
void
foo(T... t)
{
    static_assert(
        and_...>::value
        , "Invalid parameter was passed" );
    // ...
}

template<
    typename... T
    , typename = typename std::enable_if<
        and_...>::value
    >::type
>
void
foo(T... t)
{
    // ...
}

As you can see, non-type template parameters aren't used here.