C++容器array

【转自】：http://www.cnblogs.com/DswCnblog/p/5671799.html
array是一个固定大小的顺序容器，不能动态改变大小，array内的元素在内存中以严格的线性顺序存储，与普通数组声明存储空间大小[]的方式是一样有效的，只是加入了一些成员函数和全局函数[get (array)、operators (array)]，以便当作标准容器使用零大小的array是有效的，但是不可以被成员函数front、back、data间接引用
array的swap是一个线性操作交换所有的元素，通常是非常低效的

Constructor:1.template < class T, size_t N > class array;举例：array<int,10> iArray={1,2,3,4,5,6,7,8,9,10};  

Member functions:
Iterators

begin Return iterator to beginning end Return iterator to end rbegin Return reverse iterator to reverse beginning rend Return reverse iterator to reverse end cbegin Return const_iterator to beginning cend Return const_iterator to end crbegin Return const_reverse_iterator to reverse beginning crend Return const_reverse_iterator to reverse end

std::array<int,5> arr = { 2, 16, 77, 34, 50 };  std::cout << "arr contains:";  for ( auto it = arr.cbegin(); it != arr.cend(); ++it ){　　*it = 34;　　　　//error can't modify *it　　arr.begin();　　//point to array first element　　arr.front();　　//return the first element　　arr.back();　　 //return the end element　　std::cout << *it << std::endl;}

Capacity

empty Test whether list is empty size Return size max_size Return maximum size

Element access

operator[] Access element at Access element front Access first element back Access last element data Get pointer to first data

注意：使用at程序崩溃时不会显示堆栈信息，尽量使用[]去array的值

back

std::array<int,3> myarray = {5, 19, 77};  std::cout << "front is: " << myarray.front() << std::endl;   // 5  std::cout << "back is: " << myarray.back() << std::endl;     // 77  myarray.back() = 50;  for ( int& x : myarray ) 　　std::cout << " " << x;   //5 19 50

data//返回指向array中第一个元素的指针

const char* cstr = "Test string";  std::array<char,12> charray;  std::memcpy (charray.data(),cstr,12);  std::cout << charray.data() << std::endl;//如果是char类型则打印值 Test string  //如果array中保存的是int  cout << iArray.data() << endl;//两者等效，等于打印出第一个元素的地址  cout << &charray << endl;  array<string,5> sArray={"hello","c++","I"};  for (auto it = sArray.cbegin(); it != sArray.cend(); ++it)  {     cout << *it << '\t';//打印出hello  c++ I  }  cout << sArray.data() << endl;//打印地址  

Modifiers

fill Fill array with value swap Swap content

fill

std::array<int, 5> arr;arr.fill(34);for (auto it = arr.begin(); it != arr.end(); it++){    std::cout << " " << *it;}arr.assign(5);for (auto it = arr.begin(); it != arr.end(); it++){   std::cout << " " << *it;}

OutPut:
34 34 34 34 34 5 5 5 5 5

swap

std::array<int,5> first = {10, 20, 30, 40, 50};  std::array<int,5> second = {11, 22, 33, 44, 55};  first.swap (second);  std::cout << "first:";  for (int& x : first)     std::cout << " " << x;  

Global functions

get(array) Get element (tuple interface) (function template ) operators (array) Global relational operator functions for array

get(array)//Returns a reference to the Ith element of array arr.

函数原型：1.template <size_t I, class T, size_t N> T& get ( array<T,N>& arr ) noexcept;2.template <size_t I, class T, size_t N> T&& get ( array<T,N>&& arr ) noexcept;3.template <size_t I, class T, size_t N> const T& get ( const array<T,N>& arr ) noexcept;

std::array<int,3> myarray = {10, 20, 30};  std::tuple<int,int,int> mytuple (10, 20, 30);  std::tuple_element<0,decltype(myarray)>::type myelement;  // int [decltype是新标准中用来取类型]  //array头文件中重载了tuple_element和tuple_size方便和tuple交互  //交换myarray[0]和myarray[2]  myelement = std::get<2>(myarray);//取出array中的30  std::get<2>(myarray) = std::get<0>(myarray);//把array中的10换成30  std::get<0>(myarray) = myelement;//把30赋值给第一个元素  std::cout << "first element in myarray: " << std::get<0>(myarray) << "\n";  std::cout << "first element in mytuple: " << std::get<0>(mytuple) << "\n";  

Output:
first element in myarray: 30
first element in mytuple: 10

operators(array)

模板原型如下：1.template <class T, size_T N>    bool operator== ( const array<T,N>& lhs, const array<T,N>& rhs );2.template <class T, size_T N>    bool operator!= ( const array<T,N>& lhs, const array<T,N>& rhs );3.template <class T, size_T N>    bool operator< ( const array<T,N>& lhs, const array<T,N>& rhs );4template <class T, size_T N>   bool operator> ( const array<T,N>& lhs, const array<T,N>& rhs );5.template <class T, size_T N>    bool operator<= ( const array<T,N>& lhs, const array<T,N>& rhs );6.template <class T, size_T N>    bool operator>= ( const array<T,N>& lhs, const array<T,N>& rhs );

  std::array<int,5> a = {10, 20, 30, 40, 50};    std::array<int,5> b = {10, 20, 30, 40, 50};    std::array<int,5> c = {50, 40, 30, 20, 10};    if (a==b) std::cout << "a and b are equal\n";    if (b!=c) std::cout << "b and c are not equal\n";    if (b<c) std::cout << "b is less than c\n";    if (c>b) std::cout << "c is greater than b\n";    if (a<=b) std::cout << "a is less than or equal to b\n";    if (a>=b) std::cout << "a is greater than or equal to b\n";  

Output:
a and b are equal
b and c are not equal
b is less than c
c is greater than b
a is less than or equal to b
a is greater than or equal to b