C++中数组类型的操作

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。这些函数在我们需要信息或操纵不同维度的数组时非常有用。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。值得注意的是，即使是 std：：数组 根据此函数，不被视为数组。如果type为array，则“value”成员常量返回true，否则返回false。
2. 是一样的吗 此函数用于检查 类型关系 如果两种类型具有完全相同的特征，则返回true。如果类型相同，“value”成员常量返回true，否则返回false。

   // C++ code to demonstrate the working of // is_array() and is_same() #include<type_traits> #include<iostream> #include<array> #include<string> using namespace std; int main() { // checking which is array using is_array cout << "Is Integer an array? : " << is_array< int >::value << endl; cout << "Is Array an array? : " << is_array< int [10]>::value << endl; cout << "Is 2D Array an array? : " << is_array< int [10][10]>::value << endl; cout << "Is String an array? : " << is_array<string>::value << endl; cout << "Is Character Array an array? : " << is_array< char [10]>::value << endl; cout << "Is Array class type an array? : " << is_array<array< int ,3>>::value << endl; cout << endl; // checking for same types using is_same() cout << "Is 2D array same as 1D array? : " << is_same< int [10], int [10][10]>::value << endl; cout << "Is Character array same as Integer array? : " << is_same< int [10], char [10]>::value << endl; cout << "Is 1D array same as 1D array (Different sizes) ? : " << is_same< int [10], int [20]>::value << endl; cout << "Is 1D array same as 1D array? (Same sizes): " << is_same< int [10], int [10]>::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. 秩（）： 这是一个 属性查询函数 返回数组的秩。等级意味着 数组的维数 .值成员常量返回对象的秩。

   // C++ code to demonstrate the working of // rank() #include<type_traits> // for array query functions #include<iostream> using namespace std; int main() { // checking rank of different types cout << "The rank of integer is : " << rank< int >::value << endl; cout << "The rank of 1D integer array is : " << rank< int [10]>::value << endl; cout << "The rank of 2D integer array is : " << rank< int [20][10]>::value << endl; cout << "The rank of 3D integer array is : " << rank< int [20][10][40]>::value << endl; cout << "The rank of 1D character array is : " << rank< char [10]>::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. 范围（）： “范围”和“删除范围”都是 复合型蚀变 可以应用于C++中的数组。此函数返回数组的特定维度的大小。此函数接受两个参数：数组类型和必须找到其大小的维度。这也有用于打印值的成员常量值。
5. 删除_extent（）： 此函数用于删除所声明矩阵/数组中左侧的第一个维度。
6. 删除所有扩展数据块（）： 此函数用于删除矩阵/数组的所有维度，并将其转换为基本数据类型。

   // C++ code to demonstrate the working of // extent(), remove_extent(), remove_all_extents() #include<type_traits> // for array query functions #include<iostream> 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< int [20][10][40],0>::value << endl; cout << "The extent of 2nd dimension of 3D integer array is : " ; cout << extent< int [20][10][40],1>::value << endl; cout << "The extent of 3rd dimension of 3D integer array is : " ; cout << extent< int [20][10][40],2>::value << endl; cout << "The extent of 4th dimension of 3D integer array is : " ; cout << extent< int [20][10][40],3>::value << endl; cout << endl; // Removing extent of types cout << "The rank after removing 1 extent is : " ; cout << rank<remove_extent< int [20][10][30]>::type>::value << endl; // 1st dimension from left is deleted cout << "The extent of 1st after removing 1 extent is : " ; cout << extent<remove_extent< int [20][10][30]>::type>::value << endl; cout << endl; // Removing all extents of types cout << "The rank after removing all extents is : " ; cout << rank<remove_all_extents< int [20][10][30]>::type>::value << endl; // All extents are deleted cout << "The extent of 1st after removing all extents is : " ; cout << extent<remove_all_extents< int [20][10][30]>::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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