Array initialization

将数组初始化为0

Static array/ stack array

#include <iostream>
#include <algorithm>
int main()
{
    constexpr int ArraySize = 100;
    int Array[ArraySize] { };

    std::cout << std::all_of(Array, Array + ArraySize, [](int a)
    {   return a==0;}
    ) << std::endl;

}
// g++ test.cpp --std=c++11 -pedantic -Wall -Wextra

Dynamic array

#include <iostream>
#include <algorithm>
#include <memory>
int main()
{
    constexpr int ArraySize = 100;
    int *Array { new int[ArraySize] { } };

    std::cout << std::all_of(Array, Array + ArraySize, [](int a)
    {   return a==0;}
    ) << std::endl;

}
// g++ test.cpp --std=c++11 -pedantic -Wall -Wextra

stackoverflow Initializing an array of zeroes

It is well known that missing initializers for an array of scalars are defaulted to zero.

int A[5]; // Entries remain uninitialized
int B[5]= { 0 }; // All entries set to zero

But is this (below) guaranteed ?

int C[5]= { }; // All entries set to zero

A

The empty braced initialisation performs aggregation-initialization of the array: this leads to zero-initialization of the int elements.

Yes, this is guaranteed.

stackoverflow C++ array initialization

A

If you believe it improves readability, you can certainly use

bool myBoolArray[ARRAY_SIZE] = { false };
char* myPtrArray[ARRAY_SIZE] = { nullptr };

NOTE:

测试程序:

#include <iostream>
#include <algorithm>
#include <memory>
int main()
{
  constexpr int ArraySize = 100;
  bool myBoolArray[ArraySize] = { false };
  char *myPtrArray[ArraySize] = { nullptr };

  std::cout << std::all_of(myBoolArray, myBoolArray + ArraySize, [](bool a) 
  {   return a==false;}
  ) << std::endl;
  std::cout << std::all_of(myPtrArray, myPtrArray + ArraySize, [](char *a) 
  {   return a==nullptr;}
  ) << std::endl;
}
// g++ test.cpp --std=c++11 -pedantic -Wall -Wextra

输出如下:

1
1

说明数组中的所有元素都被设置为相同值了。

However, in C++ = { 0 } might not work for all types, like enum types, for example, which cannot be initialized with integral 0.

But C++ supports the shorter form

T myArray[ARRAY_SIZE] = {};

cppreference Array initialization

TODO

https://www.dummies.com/programming/cpp/initializing-an-array-in-c/

https://www.learncpp.com/cpp-tutorial/62-arrays-part-ii/

https://stackoverflow.com/questions/4057948/initializing-a-member-array-in-constructor-initializer

https://www.dummies.com/programming/cpp/initializing-an-array-in-c/

https://stackoverflow.com/questions/4057948/initializing-a-member-array-in-constructor-initializer

https://stackoverflow.com/questions/2983819/how-initialize-array-of-classes