Effective Modern C++ StudyC++ Korea

Speaker : Yun Seok-joon ( icysword77@gmail.com )

Prefer alias declarations to typedefs.

1. C++98 typedef , #define

2. C++11 using (alias declaration)

3. alias template

4. Type Trait Transformation

1. C++98 typedef, #define

Effective Modern C++ StudyC++ Korea

#define INT32 inttypedef unsigned char BYTE;typedef unsigned short WORD;

5

#define 은단순문자열치환기능 -> Debugging 힘듬

typedef 는원래타입을숨김 -> 코드이해도하락

Effective Modern C++ StudyC++ Korea

int nVal1 = 2;int nVal2 = 3;

void FUNC_SKY(int args) { std::cout << "Sky : " << args << std::endl; }void FUNC_FLY(int args) { std::cout << "Fly : " << args << std::endl; }

#define MAC_FUNC(F, N) FUNC_##F(nVal##N)

MAC_FUNC(SKY, 2); // Sky : 3

6

## : 앞뒤 문자들을 붙여서 Code에 삽입

Effective Modern C++ StudyC++ Korea

typedef basic_string<char, char_traits<char>, allocator<char>> string;

7

어떤게 더 편할까요 ?std::string strA;std::string strB;

std::basic_string<char, char_traits<char>, allocator<char>> strA;std::basic_string<char, char_traits<char>, allocator<char>> strB;

const std::_Simple_types<std::_Wrap_alloc<std::_Vec_base_types<Widget, std::allocator<Widget> >::_Alloc>::value_type>::value_type *

Effective Modern C++ StudyC++ Korea9

// C++98 typedef

typedef std::unique_ptr<std::unordered_map<std::string, std::string>> UPM_SS;

// C++11 using

using UPM_SS = std::unique_ptr<std::unordered_map<std::string, std::string>>;

에이~ 별 차이 없자나.

Effective Modern C++ StudyC++ Korea10

// C++98 typedef

typedef void(*Func)(int, const std::string&);

// using (alias declaration)

using Func = void(*)(int, const std::string&);

좀 보기 좋긴 한데…

그래도~ 별 차이 없자나.

Effective Modern C++ StudyC++ Korea12

template<typename T> // using (alias declaration)using MyList = std::list<T, MyAlloc<T>>;

template<typename T> // typedefstruct MyList{

typedef std::list<T, MyAlloc<T>> TYPE;};

MyList<Widget> LW;

MyList<Widget>::TYPE LW;

선언이 좀 불편하긴 하네.

근데 사용은 더 불편하다.

Effective Modern C++ StudyC++ Korea14

template 타입의 속성을 변화

std::remove_const<T>::type // T from const Tstd::remove_reference<T>::type // T from T&, T&&std::add_lvalue_reference<T>::type // T& from T

::type ?

누가봐도 template struct typedef 사용한것임을 알수 있다.

Effective Modern C++ StudyC++ Korea15

std::remove_const_t<T> // T from const Tstd::remove_reference_t<T> // T from T&, T&&std::add_lvalue_reference_t<T> // T& from T

이름이 중복 되니깐 _t를 붙여서 사용

Effective Modern C++ StudyC++ Korea16

template<class T>using remove_const_t = typename std::remove_const<T>::type;

template<class T>using remove_refernece_t = typename std::remove_reference_t<T>::type;

template<class T>using add_lvalue_reference_t

= typename std::add_lvalue_reference<T>::type;

Effective Modern C++ StudyC++ Korea17

http://www.cplusplus.com/reference/type_traits

…

Effective Modern C++ StudyC++ Korea19

• using (별칭선언)은 template를 지원합니다.

• using은 ::type 을 뒤에 붙일 필요도 없고,

typename 을 앞에 붙일 필요도 없습니다.

• C++14에서는 C++11의 Type Trait Transformation을

별칭 선언으로 지원합니다.

http://devluna.blogspot.kr/2015/03/item-9-typedef.html

icysword77@gmail.com