C++中的数组类型操作

本文演示了一些内置函数，这些函数可用于查询和操作数组类型，甚至是多维数组。在我们需要信息或操纵以不同维度启动的数组的情况下，这些功能很有用。这些函数在头文件中定义。其中一些功能包括：

1. is_array()：顾名思义，此函数的唯一目的是检查变量是否为数组类型。在此值得注意的是，根据此函数，即使std :: array也不会被视为数组。如果类型为数组，则“值”成员常量将返回true，否则返回false。
2. is_same()：此函数用于检查类型关系，如果两个类型具有完全相同的特征，则返回true。如果类型相同，则“值”成员常量将返回true，否则返回false。

   // C++ code to demonstrate the working of 
   // is_array() and is_same()
     
   #include
   #include
   #include
   #include
   using namespace std;
     
   int main()
   {
       // checking which is array using is_array
       cout << "Is Integer an array? : " << is_array::value << endl;
         
       cout << "Is Array an array? : " << is_array::value << endl;
         
       cout << "Is 2D Array an array? : " 
       << is_array::value << endl;
         
       cout << "Is String an array? : " << is_array::value << endl;
         
       cout << "Is Character Array an array? : " 
       << is_array::value << endl;
         
       cout << "Is Array class type an array? : " 
       << is_array>::value << endl;
         
       cout << endl;
         
       // checking for same types using is_same()
       cout << "Is 2D array same as 1D array? : " << 
       is_same::value << endl;
         
       cout << "Is Character array same as Integer array? : " 
       << is_same::value << endl;
         
       cout << "Is 1D array same as 1D array (Different sizes) ? : " 
       << is_same::value << endl;
         
       cout << "Is 1D array same as 1D array? (Same sizes): " 
       << is_same::value << endl;
       return 0;
   }
   

   输出：

   Is Integer an array? : 0
   Is Array an array? : 1
   Is 2D Array an array? : 1
   Is String an array? : 0
   Is Character Array an array? : 1
   Is Array class type an array? : 0
   
   Is 2D array same as 1D array? : 0
   Is Character array same as Integer array? : 0
   Is 1D array same as 1D array (Different sizes) ? : 0
   Is 1D array same as 1D array? (Same sizes): 1
   

3. rank()：这是一个属性查询函数，它返回数组的秩。等级是指数组的维数。值成员常量返回对象的等级。

   // C++ code to demonstrate the working of 
   // rank()
     
   #include // for array query functions
   #include
   using namespace std;
     
   int main()
   {
       // checking rank of different types
       cout << "The rank of integer is : " << rank::value << endl;
         
       cout << "The rank of 1D integer array is : " 
       << rank::value << endl;
         
       cout << "The rank of 2D integer array is : " 
       << rank::value << endl;
         
       cout << "The rank of 3D integer array is : " 
       << rank::value << endl;
         
       cout << "The rank of 1D character array is : " 
       << rank::value << endl;
     
       cout << endl;
         
   }
   

   输出：

   The rank of integer is : 0
   The rank of 1D integer array is : 1
   The rank of 2D integer array is : 2
   The rank of 3D integer array is : 3
   The rank of 1D character array is : 1
   

4. scope()：扩展范围和删除扩展都是化合物类型的更改，可以应用于C++中的数组。此函数返回数组特定维的大小。此函数接受两个参数，即数组类型和必须找到其大小的维。这也具有用于打印值的成员常数值。
5. remove_extent()：此函数从声明的矩阵/数组中从左侧移除第一个维度。
6. remove_all_extents()：此函数删除矩阵/数组的所有维，并将其转换为基础数据类型。

   // C++ code to demonstrate the working of 
   // extent(), remove_extent(), remove_all_extents()
     
   #include // for array query functions
   #include
   using namespace std;
     
   int main()
   {
     
         
       // Checking extent of different types (using extent)
       cout << "The extent of 1st dimension of 3D integer array is : " ;
       cout << extent::value << endl;
         
       cout << "The extent of 2nd dimension of 3D integer array is : " ;
       cout << extent::value << endl;
         
       cout << "The extent of 3rd dimension of 3D integer array is : " ;
       cout << extent::value << endl;
         
       cout << "The extent of 4th dimension of 3D integer array is : " ;
       cout << extent::value << endl;
         
       cout << endl;
         
       // Removing extent of types
       cout << "The rank after removing 1 extent is : " ;
       cout << rank::type>::value << endl;
         
       // 1st dimension from left is deleted
       cout << "The extent of 1st after removing 1 extent is : " ;
       cout << extent::type>::value << endl;
         
       cout << endl;
         
       // Removing all extents of types
       cout << "The rank after removing all extents is : " ;
       cout << rank::type>::value << endl;
         
       // All extents are deleted
       cout << "The extent of 1st after removing all extents is : " ;
       cout << extent::type>::value << endl;
     
       cout << endl;
         
   }
   

   输出：

   The extent of 1st dimension of 3D integer array is  : 20
   The extent of 2nd dimension of 3D integer array is  : 10
   The extent of 3rd dimension of 3D integer array is  : 40
   The extent of 4th dimension of 3D integer array is  : 0
   
   The rank after removing 1 extent is : 2
   The extent of 1st after removing 1 extent is : 10
   
   The rank after removing all extents is : 0
   The extent of 1st after removing all extents is : 0
   

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