Answers for "new operator c++"

new c++

MyClass * p1 = new MyClass;
      // allocates memory by calling: operator new (sizeof(MyClass))
      // and then constructs an object at the newly allocated space

  MyClass * p2 = new (std::nothrow) MyClass;
      // allocates memory by calling: operator new (sizeof(MyClass),std::nothrow)
      // and then constructs an object at the newly allocated space

  new (p2) MyClass;
      // does not allocate memory -- calls: operator new (sizeof(MyClass),p2)
      // but constructs an object at p2

  // Notice though that calling this function directly does not construct an 
  //object:
  MyClass * p3 = (MyClass*) ::operator new (sizeof(MyClass));
      // allocates memory by calling: operator new (sizeof(MyClass))
      // but does not call MyClass's constructor

  delete p1;
  delete p2;
  delete p3;

new keyword in cpp

#include <iostream>
#include <string>

using String = std::string;
class Entity
{
private:
	String m_Name;
public:
	Entity() : m_Name("Unknown") {}
	Entity(const String& name) : m_Name(name) {}
	const String& GetName() const {
		return m_Name;
	};
};
int main() {
  // new keyword is used to allocate memory on heap
	int* b = new int; // new keyword will call the c function malloc which will allocate on heap  memory = data and return a ptr to that plaock of memory
	int* c = new int[50];
	Entity* e1 = new Entity;//new keyword Not allocating only memory but also calling the constructor
	Entity* e = new Entity[50];
	//usually calling new will  call underlined c function malloc
	//malloc(50); 
	Entity* alloc = (Entity*)malloc(sizeof(Entity));//will not call constructor only  allocate memory = memory of entity
	delete e;//calls a c function free
	Entity* e3 = new(c) Entity();//Placement New
}

operator c++

Common operators
assignment | increment | arithmetic |  logical | comparison | member | other
		   | decrement |            |		   |		    | access |
-----------------------------------------------------------------------------                            
  a = b    |    ++a    |     +a	    |	 !a	   |   a == b   |  a[b]  | a(...)
  a += b   |	--a	   |     -a		|  a && b  |   a != b   |   *a   |  a, b
  a -= b   |	a++	   |   a + b	|  a || b  |   a < b    |   &a   |  ? :
  a *= b   |	a--	   |   a - b	|	       |   a > b    |  a->b  |
  a /= b   |		   |   a * b	|	       |   a <= b	|  a.b   |
  a %= b   |		   |   a / b	|		   |   a >= b	|  a->*b |
  a &= b   |		   |   a % b	|		   |   a <=> b	|  a.*b  |
  a |= b   |		   |     ~a		|		   |		    |		 |
  a ^= b   |		   |   a & b	|		   |   		    |		 |
  a <<= b  |		   |   a | b	|		   |			|		 |
  a >>= b  |		   |   a ^ b	|		   |			|		 |     
   		   |		   |   a << b	|		   |			|		 |  
     	   |		   |   a >> b	|		   |			|		 |

new in c++

#include <iostream>
#include <string>

using String = std::string;
class Entity
{
private:
	String m_Name;
public:
	Entity() : m_Name("Unknown") {}
	Entity(const String& name) : m_Name(name) {}
	const String& GetName() const {
		return m_Name;
	};
};
int main() {
  // new keyword is used to allocate memory on heap
	int* b = new int; // new keyword will call the c function malloc which will allocate on heap  memory = data and return a ptr to that plaock of memory
	int* c = new int[50];
	Entity* e1 = new Entity;//new keyword Not allocating only memory but also calling the constructor
	Entity* e = new Entity[50];
	//usually calling new will  call underlined c function malloc
	//malloc(50); 
	Entity* alloc = (Entity*)malloc(sizeof(Entity));//will not call constructor only  allocate memory = memory of entity
	delete e;//calls a c function free
	Entity* e3 = new(c) Entity();//Placement New

operator in c++

2x in c++