function pointer c 2b 2b

1int myvar = 6;
2int pointer = &myvar; // adress of myvar
3int value = *pointer; // the value the pointer points to: 6

1#include <iostream>
2
3using namespace std;
4
5int main () {
6   int  var = 20;   // actual variable declaration.
7   int  *ip;        // pointer variable 
8
9   ip = &var;       // store address of var in pointer variable
10
11   cout << "Value of var variable: "; 
12   cout << var << endl; //Prints "20"
13
14   // print the address stored in ip pointer variable
15   cout << "Address stored in ip variable: ";
16   cout << ip << endl; //Prints "b7f8yufs78fds"
17
18   // access the value at the address available in pointer
19   cout << "Value of *ip variable: ";
20   cout << *ip << endl; //Prints "20"
21
22   return 0;
23}

1Every object in C++ has access to its own address through an important pointer called this pointer.
2 The this pointer is an implicit parameter to all member functions. 
3Therefore, inside a member function,
4 this may be used to refer to the invoking object.
5
6Friend functions do not have a this pointer,
7 because friends are not members of a class. 
8Only member functions have a this pointer.

1void simple_pointer_examples() {
2    int   a;  // a can contain an integer
3	int*  x;  // x can contain the memory address of an integer. 
4 	char* y;  // y can contain the memory address of a char. 
5 	Foo*  z;  // z can contain the memory address of a Foo object.  
6 
7    a = 10;
8    x = &a;   // '&a' extracts address of a 
9  
10    std::cout <<  x << std::endl; // memory address of a => 0x7ffe9e25bffc
11    std::cout << *x << std::endl; //          value of a => 10
12}

1void one() { cout << "One\n"; }
2void two() { cout << "Two\n"; }
3
4
5int main()
6{
7	void (*fptr)(); //Declare a function pointer to voids with no params
8
9	fptr = &one; //fptr -> one
10	*fptr(); //=> one()
11
12	fptr = &two; //fptr -> two
13	*fptr(); //=> two()
14
15	return 0;
16}
17

1#include <iostream>
2
3using namespace std;
4// isualize this on http://pythontutor.com/cpp.html#mode=edit
5int main()
6{
7   double* account_pointer = new double;
8   *account_pointer = 1000;
9   cout << "Allocated one new variable containing " << *account_pointer
10      << endl;
11   cout << endl;
12
13   int n = 10;
14   double* account_array = new double[n];
15   for (int i = 0; i < n; i++)
16   {
17      account_array[i] = 1000 * i;
18   }   
19   cout << "Allocated an array of size " << n << endl;
20   for (int i = 0; i < n; i++)
21   {
22      cout << i << ": " << account_array[i] << endl;
23   }
24   cout << endl;
25
26   // Doubling the array capacity 
27   double* bigger_array = new double[2 * n];
28   for (int i = 0; i < n; i++)
29   {
30      bigger_array[i] = account_array[i];
31   }
32   delete[] account_array; // Deleting smaller array
33   account_array = bigger_array;
34   n = 2 * n;
35
36   cout << "Now there is room for an additional element:" << endl;
37   account_array[10] = 10000;
38   cout << 10 << ": " << account_array[10] << endl;    
39   
40   delete account_pointer;
41   delete[] account_array; // Deleting larger array
42   
43   return 0;
44}