C++11 容器Array

array是一個固定大小的順序容器，不能動態改變大小，array內的元素在內存中以嚴格的線性順序存儲
與普通數組聲明存儲空間大小[]的方式是一樣有效的，只是加入了一些成員函數和全局函數[get (array)、operators (array)]，以便當作標准容器使用
零大小的array是有效的，但是不可以被成員函數front、back、data間接引用
array的swap是一個線性操作交換所有的元素，通常是非常低效的

Constructor:
1.template < class T, size_t N > class array;

舉例：
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程序崩潰時不會顯示堆棧信息，盡量使用[]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中第一個元素的指針

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類型則打印值 Test string  
//如果array中保存的是int  
cout << iArray.data() << endl;//兩者等效，等於打印出第一個元素的地址  
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.

函數原型：
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是新標准中用來取類型]  
//array頭文件中重載了tuple_element和tuple_size方便和tuple交互  
//交換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換成30  
std::get<0>(myarray) = myelement;//把30賦值給第一個元素  
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