// in C++03:
// typedef /* compute */ result;
using result = and_<is_integral<T>, not_<is_char<T>>>;

// Enforce precondition: every type T must be integral
static_assert( and_<std::is_integral<T>...>::value, "Violation" );

template <typename T,
          EnableIf<is_scalable<T>, is_something_else<T>>...>
T twice(T t) { return 2*t; }

template<typename T>
typename enable_if<
    and_<is_scalable<T>, is_something_else<T>>
    , T
>::type twice(T t) { return 2*t; }

template<typename T>
typename std::enable_if<
    is_scalable<T>::value && is_something_else<T>::value
    , T
>::type twice(T t) { return 2*t; }

// EnableIf alias now accepts non-type template parameters
template<typename T
         , EnableIf<is_scalable<T>() && is_something_else<T>()>...>
T twice(T t) { return 2*t; }

is_integral<T>::value && !is_char<T>::value

template<typename T>
struct is_integral_and_not_char {
    static const bool value = is_integral<T>::value && !is_char<T>::value;
};

is_integral_and_not_char<T>::value

template<typename T>
struct is_integral_and_not_char
  : std::integral_constant<bool, std::is_integral<T>::value && !std::is_char<T>::value>
{}