【SFINAE】可変リストによるテンプレート関数の優先実体化 ref: http://qiita.com/Riyaaaa_a/items/a156383f640263f35985

file0.cpp

template<class T> struct is_const : public std::false_type {};
template<class T> struct is_const<T const> : public std::true_type {};

file1.cpp

#include <type_traits>
#include <iostream>

template<class T>
auto printBasicType() 
-> typename std::enable_if<std::is_null_pointer<T>{}>::type
{
    std::cout << "null pointer" << std::endl;
}

template<class T>
auto printBasicType() 
-> typename std::enable_if<std::is_array<T>{}>::type
{
    std::cout << "array" << std::endl;
}

template<class T>
auto printBasicType() 
-> typename std::enable_if<std::is_integral<T>{}>::type
{
    std::cout << "integral" << std::endl;
}

template<class T>
auto printBasicType() 
-> typename std::enable_if<std::is_class<T>{}>::type
{
    std::cout << "class" << std::endl;
}

int main() {
    class Hoge {};
    printBasicType<std::nullptr_t>();
    printBasicType<int>();
    printBasicType<int[]>();
    printBasicType<Hoge>();
    return 0;
}

file2.cpp

extern void* enabler;

template<class T, typename std::enable_if<std::is_null_pointer<T>{}>::type*& = enabler>
void printBasicType() 
{
    std::cout << "null pointer" << std::endl;
}

//...同様

file3.cpp

template<class T, typename std::enable_if<std::is_null_pointer<T>{}, std::nullptr_t>::type = nullptr>
void printBasicType() 
{
    std::cout << "null pointer" << std::endl;
}

file4.cpp

template<typename T, typename = decltype(std::declval<T>().hoge())>
struct has_hoge : std::true_type {};

template<typename T>
struct has_hoge : std::false_type {};

file5.cpp

template<class T>
struct has_hoge {
    template<typename U = T, typename = decltype(std::declval<U>().hoge()) >
    static std::true_type test();
    static std::false_type test();
};

file6.cpp

void test(...);
template<typename Args...>
void test(Args... args);

file7.cpp

#include <type_traits>

template<class T>
struct has_hoge {
    template<typename U = T, typename = decltype(std::declval<U>().hoge()) >
    static std::true_type test(int);
    static std::false_type test(...);
};

int main() {
    struct piyo {
        bool hoge(){ return true; }
    };

    static_assert(decltype(has_hoge<piyo>::test(0)){}, "!!");
    static_assert(!decltype(has_hoge<int>::test(0)){}, "!!");

    return 0;
}

file8.cpp

template<class T>
struct identity {
  typedef T type;
};

//...
static_assert(identity<decltype(has_hoge<piyo>::test(0))>::type::value, "!!");