[SOLVED] CS // from: https://en.cppreference.com/w/cpp/language/value_initialization

// from: https://en.cppreference.com/w/cpp/language/value_initialization

#include
#include
#include

struct T1
{
int mem1;
std::string mem2;
}; // implicit default constructor

struct T2
{
int mem1;
std::string mem2;
T2(const T2&) { } // user-provided copy constructor
};// no default constructor

struct T3
{
int mem1;
std::string mem2;
T3() { } // user-provided default constructor
};

std::string s{}; // class => default-initialization, the value is

int main()
{
int a1 {1}; // direct initialization
int a2 = {2}; // copy initialization
int a3 = 3; // copy initialization
int a4(4);// direct initialization

int n{};// scalar => zero-initialization, the value is 0
double f = double();// scalar => zero-initialization, the value is 0.0
int* a = new int[10](); // array => value-initialization of each element
//the value of each element is 0
T1 t1{};// class with implicit default constructor =>
// t1.mem1 is zero-initialized, the value is 0
// t1.mem2 is default-initialized, the value is
//T2 t2{};// error: class with no default constructor
T3 t3{};// class with user-provided default constructor =>
// t3.mem1 is default-initialized to indeterminate value
// t3.mem2 is default-initialized, the value is
std::vector v(3);// value-initialization of each element
// the value of each element is 0
T1 t1v2 = { 99,hi };// aggregate initialization struct has no user-defined constructors):
// assigns listed values sequentially to declared members
//T2 t2v2 = { 99,hi };// aggregate initialization: illegal -> struct has explicitly defined default constructor
//T3 t3v2 = { 99,hi };// aggregate initialization: illegal -> struct has explicitly defined constructor

std::cout << a1 << a2 << a3 << a4 << ‘
‘;std::cout << s.size() << ‘ ‘ << n << ‘ ‘ << f << ‘ ‘ << a[9] << ‘ ‘ << v[2] << ‘
‘;std::cout << t1.mem1 << ‘ ‘ << t3.mem1 << ‘
‘;std::cout << t1v2.mem1 << ‘ ‘ << t1v2.mem2 << ‘
‘;delete[] a;}