Function pointer C++

#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; }

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

void simple_pointer_examples() { int a; // a can contain an integer int* x; // x can contain the memory address of an integer. char* y; // y can contain the memory address of a char. Foo* z; // z can contain the memory address of a Foo object. a = 10; x = &a; // '&a' extracts address of a std::cout << x << std::endl; // memory address of a => 0x7ffe9e25bffc std::cout << *x << std::endl; // value of a => 10 }

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; }

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;
}

Posted by: Guest on April-02-2020

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