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使用c++11改写loki的TypeList

文章编辑:2138com太阳集团 时间:2016年11月08日

  最近看了C++11的一些特性,最感兴趣的是可变模板参数,自动类型推断和匿名函数。

  Loki中的TypeList,是需要递归定义的,并且需要一个NullType作为尾节点。

  可变模板参数使得实现TypeList更简洁,更易懂。

  以下是我用C++11实现TypeList。

  复制代码

  //////////////////////////////////////////////////////////

  template<typename... TList>

  struct typelist

  {

  };

  typedef typelist<> nulllist;

  //////////////////////////////////////////////////////////

  template<typename... TList> struct length;

  template<typename... TList>

  struct length< typelist<TList...> >

  {

  enum { value = sizeof...(TList) };

  };

  //////////////////////////////////////////////////////////

  template<typename T, typename... TList> struct push_front;

  template<typename T, typename... TList>

  struct push_front< T, typelist<TList...> >

  {

  typedef typelist<T, TList...>  type;

  };

  //////////////////////////////////////////////////////////

  template<typename... TList> struct pop_front;

  template<typename T, typename... TList>

  struct pop_front< typelist<T, TList...> >

  {

  typedef typelist<TList...> type;

  };

  template<>

  struct pop_front< nulllist >

  {

  typedef nulllist type;

  };

  //////////////////////////////////////////////////////////

  template<unsigned int N, typename... TList> struct at;

  template<unsigned int N, typename T, typename... TList>

  struct at< N, typelist<T, TList...> >

  {

  typedef typename at< N-1, typelist<TList...> >::type type;

  };

  template<typename T, typename... TList>

  struct at< 0, typelist<T, TList...> >

  {

  typedef T type;

  };

  template<>

  struct at< 0, nulllist >

  {

  typedef nulllist type;

  };

  //////////////////////////////////////////////////////////

  template<int A, int B>

  struct IndexFixer

  {

  enum { value = (A == B) ? B : A + 1 };

  };

  //////////////////////////////////////////////////////////

  template<typename T, typename... TList> struct indexof;

  template<typename T, typename H, typename... TList>

  struct indexof< T, typelist<H, TList...> >

  {

  enum { value = IndexFixer<indexof<T, typelist<TList...>>::value, -1>::value };

  };

  template<typename T, typename... TList>

  struct indexof< T, typelist<T, TList...> >

  {

  enum { value = 0 };

  };

  template<typename T>

  struct indexof< T, nulllist >

  {

  enum { value = -1 };

  };

  //////////////////////////////////////////////////////////

  template<typename A, typename B> struct concat;

  template<typename... A, typename... B>

  struct concat<typelist<A...>, typelist<B...> >

  {

  typedef typelist<A..., B...> type;

  };

  template<typename T, typename... TList>

  struct concat<typelist<TList...>, T >

  {

  typedef typelist<TList..., T> type;

  };

  template<typename T, typename... TList>

  struct concat< T, typelist<TList...> >

  {

  typedef typelist<T, TList...>  type;

  };

  //////////////////////////////////////////////////////////

  template<typename T, typename... TList> struct erase;

  template<typename T, typename H, typename... TList>

  struct erase<T, typelist<H, TList...> >

  {

  typedef typename concat<H, typename erase< T, typelist<TList...> >::type>::type type;

  };

  template<typename T, typename... TList>

  struct erase<T, typelist<T, TList...> >

  {

  typedef typelist<TList...> type;

  };

  template<typename T>

  struct erase<T, nulllist >

  {

  typedef nulllist type;

  };

  //////////////////////////////////////////////////////////

  template<typename T, typename... TList> struct erase_all;

  template<typename T, typename H, typename... TList>

  struct erase_all<T, typelist<H, TList...> >

  {

  typedef typename concat<H, typename erase_all< T, typelist<TList...> >::type>::type type;

  };

  template<typename T, typename... TList>

  struct erase_all<T, typelist<T, TList...> >

  {

  typedef erase_all< T,typelist<TList...> > type;

  };

  template<typename T, typename U>

  struct erase_all<T, typelist<U> >

  {

  typedef U type;

  };

  template<typename T>

  struct erase_all<T, nulllist >

  {

  typedef nulllist type;

  };

  //////////////////////////////////////////////////////////

  template<typename T, typename...TList> struct no_duplicate;

  template<typename T, typename...TList>

  struct no_duplicate< typelist<T, TList...> >

  {

  private:

  typedef typename no_duplicate< typelist<TList...> >::type inner;

  typedef typename erase<T, inner>::type inner_result;

  public:

  typedef typename concat<T, inner_result>::type type;

  };

  template<>

  struct no_duplicate< nulllist >

  {

  typedef nulllist type;

  };

  //////////////////////////////////////////////////////////

  template<typename R, typename T, typename...TList> struct replace;

  template<typename R, typename T, typename H, typename...TList>

  struct replace<R, T, typelist<H, TList...> >

  {

  typedef typename concat<H, typename replace<R, T, typelist<TList...>>::type>::type type;

  };

  template<typename R, typename H, typename...TList>

  struct replace<R, H, typelist<H, TList...> >

  {

  typedef typename concat<R, typelist<TList...> >::type type;

  };

  template<typename R, typename T>

  struct replace<R, T, nulllist >

  {

  typedef nulllist type;

  };

  //////////////////////////////////////////////////////////

  template<typename R, typename T, typename...TList> struct replace_all;

  template<typename R, typename T, typename H, typename...TList>

  struct replace_all<R, T, typelist<H, TList...> >

  {

  typedef typename concat<H, typename replace_all<R, T, typelist<TList...>>::type>::type type;

  };

  template<typename R, typename H, typename...TList>

  struct replace_all<R, H, typelist<H, TList...> >

  {

  typedef typename concat<R, typename replace_all<R, H, typelist<TList...>>::type >::type type;

  };

  template<typename R, typename T>

  struct replace_all<R, T, nulllist >

  {

  typedef nulllist type;

  };

  //////////////////////////////////////////////////////////

  template<typename T, typename...TList> struct reverse;

  template<typename T, typename...TList>

  struct reverse<typelist<T, TList...> >

  {

  typedef typename concat<typename reverse<typelist<TList...>>::type, T>::type type;

  };

  template<>

  struct reverse< nulllist >

  {

  typedef nulllist type;

  };

  复制代码

  例子:

  复制代码

  #include <iostream>

  #include <vector>

  #include "TypeList.h"#include <type_traits>

  using namespace hi::mpl;

  int main()

  {

  typedef typelist<int, float, bool, float> testlist;

  typedef typelist<float, bool> tlist;

  typedef typelist<int, float> hlist;

  typedef typelist<> elist;

  typedef typelist<int> ilist;

  typedef testlist mylist;

  std::cout << "length: " << length<mylist>::value << std::endl;

  bool b;

  b = std::is_same<at<2, mylist>::type, bool>::value;

  std::cout << "is same: " << b << std::endl;

  b = std::is_same<push_front<int, elist>::type, ilist>::value;

  std::cout << "is same: " << b << std::endl;

  std::cout << "indexof : " << indexof<bool, mylist>::value << std::endl;

  b = std::is_same<pop_front<typelist<>>::type, pop_front<ilist>::type>::value ;

  std::cout << "is same: " << b << std::endl;

  b = std::is_same< erase<bool, mylist>::type, typelist<int, float, float>>::value;

  std::cout << "is same: " << b << std::endl;

  b = std::is_same< no_duplicate<mylist>::type, typelist<int, float, bool>>::value;

  std::cout << "is same: " << b << std::endl;

  b = std::is_same< replace<double, bool, mylist>::type, typelist<int, float, double, float>>::value;

  std::cout << "is same: " << b << std::endl;

  b = std::is_same< replace_all<double, float, mylist>::type, typelist<int, double, bool, double>>::value;

  std::cout << "is same: " << b << std::endl;

  b = std::is_same< reverse<mylist>::type, typelist<float, bool, float, int>>::value;

  std::cout << "is same: " << b << std::endl;

  //std::cout << "is same: " << CompileTimeCount(int) << std::endl;

  //std::cout << "is same: " << CompileTimeCount(int) << std::endl;

  return 0;

  }


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