pointer function c++ code example

Example 1: c++ pointers

#include <iostream>

using namespace std;

int main () {
   int  var = 20;   // actual variable declaration.
   int  *ip;        // pointer variable 

   ip = &var;       // store address of var in pointer variable

   cout << "Value of var variable: "; 
   cout << var << endl; //Prints "20"

   // print the address stored in ip pointer variable
   cout << "Address stored in ip variable: ";
   cout << ip << endl; //Prints "b7f8yufs78fds"

   // access the value at the address available in pointer
   cout << "Value of *ip variable: ";
   cout << *ip << endl; //Prints "20"

   return 0;
}

Example 2: c++ pointers

#include <iostream>

using namespace std;
// isualize this on http://pythontutor.com/cpp.html#mode=edit
int main()
{
   double* account_pointer = new double;
   *account_pointer = 1000;
   cout << "Allocated one new variable containing " << *account_pointer
      << endl;
   cout << endl;

   int n = 10;
   double* account_array = new double[n];
   for (int i = 0; i < n; i++)
   {
      account_array[i] = 1000 * i;
   }   
   cout << "Allocated an array of size " << n << endl;
   for (int i = 0; i < n; i++)
   {
      cout << i << ": " << account_array[i] << endl;
   }
   cout << endl;

   // Doubling the array capacity 
   double* bigger_array = new double[2 * n];
   for (int i = 0; i < n; i++)
   {
      bigger_array[i] = account_array[i];
   }
   delete[] account_array; // Deleting smaller array
   account_array = bigger_array;
   n = 2 * n;

   cout << "Now there is room for an additional element:" << endl;
   account_array[10] = 10000;
   cout << 10 << ": " << account_array[10] << endl;    
   
   delete account_pointer;
   delete[] account_array; // Deleting larger array
   
   return 0;
}

Example 3: pointer in c++

int* pointVar, var;
var = 5;

// assign address of var to pointVar
pointVar = &var;

// access value pointed by pointVar
cout << *pointVar << endl;   // Output: 5

In the above code, the address of var is assigned to the pointVar pointer.
We have used the *pointVar to get the value stored in that address.

Example 4: Function pointer C++

void one() { cout << "One\n"; }
void two() { cout << "Two\n"; }


int main()
{
	void (*fptr)(); //Declare a function pointer to voids with no params

	fptr = &one; //fptr -> one
	*fptr(); //=> one()

	fptr = &two; //fptr -> two
	*fptr(); //=> two()

	return 0;
}

Example 5: c function pointer

//Declaration of a pointer to a function that takes an integer 
//and returns an integer.
int (*f_ptr)(int);

//Assignment of a function foo to the function pointer f_ptr declared above.
f_ptr = foo;

//Calling foo indirectly via f_ptr, passing the return value of foo to r.
int r = f_ptr(v);

//Assigning an address of a function to the function pointer f_ptr,
//then calling foo by dereferencing the function pointer.  
f_ptr = &foo;
int r = (*f_ptr)(v);

Example 6: pointers c++

baz = *foo;