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法学C++数组类型操作
数组是C++中一种数据结构，用于在连续的内存位置存储多个相同数据类型的元素。
在C++编程语言中，有一些内置函数可以用来操作数组类型。一些函数也可以应用于多维数组。数组头文件包含用于操作C++编程语言中数组的函数。
一些在C++中操作数组的常用方法：
is_array()
此函数用于检查传递给函数的变量是否为数组类型。此方法在识别数组方面非常严格，甚至连std::array也会被拒绝。返回类型为整数，即如果传递的是数组则返回true(1)，否则返回False (0)。
示例
#include<type_traits>
#include<iostream>
#include<array>
#include<string>
using namespace std;
int main(){
cout<<"Checking if int is an array ? : ";
is_array<int>::value?cout<<"True":cout<<"False";
cout<<"\nChecking if int[] is an array? : ";
is_array<int[6]>::value?cout<<"True":cout<<"False";
cout<<"\nChecking if 2D Array is an array? : ";
is_array<int[2][3]>::value?cout<<"True":cout<<"False";
cout<<"\nChecking if String is an array? : ";
is_array<string>::value?cout<<"True":cout<<"False";
cout<<"\nChecking if Character Array is an array? : ";
is_array<char[4]>::value?cout<<"True":cout<<"False";
cout << endl;
return 0;
}输出
Checking if int is an array ? : False Checking if int[] is an array? : True Checking if 2D Array is an array? : True Checking if String is an array? : False Checking if Character Array is an array? : True
is_same()
此函数用于检查传递的两种类型是否具有完全相同的蓝图，即两种类型的类型应该相同。让我们来看这个例子，它将阐明这个概念：
示例
#include<type_traits>
#include<iostream>
#include<array>
#include<string>
using namespace std;
int main(){
cout << "Checking if 1D array is same as 1D array (Different sizes) ? : " ;
is_same<int[3],int[4]>::value?cout<<"True":cout<<"False";
cout << "\nChecking if 1D array is same as 1D array? (Same sizes): " ;
is_same<int[5],int[5]>::value?cout<<"True":cout<<"False";
cout << "\nChecking If 2D array is same as 1D array? : ";
is_same<int[3],int[3][4]>::value?cout<<"True":cout<<"False";
cout << "\nChecking if Character array is same as Integer array? : " ;
is_same<int[5],char[5]>::value?cout<<"True":cout<<"False";
return 0;
}输出
Checking if 1D array is same as 1D array (Different sizes) ? : False Checking if 1D array is same as 1D array? (Same sizes): True Checking If 2D array is same as 1D array? : False Checking if Character array is same as Integer array? : False
rank()
rank函数用于返回传递的数组的秩。秩表示数组的维数。它返回数组秩的整数值。
示例
#include<type_traits>
#include<iostream>
using namespace std;
int main(){
cout<<"Print rank for the following types of arrays : \n";
cout<<"integer : "<<rank<int>::value<<endl;
cout<<"1D integer array (int[]) : "<< rank<int[5]>::value<<endl;
cout<<"2D integer array (int[][]) : "<<rank<int[2][2]>::value<<endl;
cout<<"3D integer array (int[][][]) : "<<rank<int[2][3][4]>::value<<endl;
cout<<"1D character array : "<<rank<char[10]>::value<<endl;
}输出
Print rank for the following types of arrays : integer : 0 1D integer array (int[]) : 1 2D integer array (int[][]) : 2 3D integer array (int[][][]) : 3 1D character array : 1
extent()
C++中的extent()方法返回数组某一维的大小。此方法有两个输入参数：数组和维数。
示例
#include<type_traits>
#include<iostream>
using namespace std;
int main(){
cout<<"Printing the length of all dimensions of the array arr[2][45][5] :\n";
cout<<"1st dimension : "<<extent<int[2][45][5],0>::value<<endl;
cout<<"2nd dimension : "<<extent<int[2][45][5],1>::value<<endl;
cout<<"3rd dimension : "<<extent<int[2][45][5],2>::value<<endl;
cout<<"4th dimension : "<<extent<int[2][45][5],3>::value<<endl;
}输出
Printing the length of all dimensions of the array arr[2][45][5] : 1st dimension : 2 2nd dimension : 45 3rd dimension : 5 4th dimension : 0
remove_extent()
remove_extent函数用于删除多维数组的维数。它删除数组的第一维。
示例
#include<type_traits>
#include<iostream>
using namespace std;
int main(){
cout<<"Removing extent of the array arr[2][5][4] : \n";
cout<<"Initial rank : "<<rank<int[2][5][4]>::value<<endl;
cout<<"The rank after removing 1 extent is : " ;
cout << rank<remove_extent<int[20][10][30]>::type>::value << endl;
cout << "length of 1st dimension after removal is :";
cout<<extent<remove_extent<int[20][10][30]>::type>::value << endl;
}输出
Removing extent of the array arr[2][5][4] : Initial rank : 3 The rank after removing 1 extent is : 2 length of 1st dimension after removal is :10
remove_all_extents()
此函数用于一次性删除数组的所有维数。数组将更改为与数组相同的变量。
示例
#include<type_traits>
#include<iostream>
using namespace std;
int main(){
cout<<"Removing all extents of the array arr[2][5][4] : \n";
cout<<"Initial rank : "<<rank<int[2][5][4]>::value<<endl;
cout<<"The rank after removing all extents is : " ;
cout << rank<remove_all_extents<int[20][10][30]>::type>::value << endl;
cout << "length of 1st dimension after removal is :";
cout<<extent<remove_all_extents<int[20][10][30]>::type>::value << endl;
}输出
Removing all extents of the array arr[2][5][4] : Initial rank : 3 The rank after removing all extents is : 0 length of 1st dimension after removal is :0
更新于：2019年10月24日
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