CPP

c++ pointers and functions

#include <iostream>

using namespace std;

void increment(int *n){  		//declare argument of the functon as pointer
    *n+=1;
   cout<<"In function: "<<*n<<endl; 
}

int main()
{
   int x=5;			
   increment(&x);		//passing the address of the variable to the function
   cout<<"In main: "<<x<<endl;
   
}

c++ function as pointer

// c++ function as pointer syntax
type(*function_name)(params...){
 	// body
}

why do we use pointers in c++

//why do we use pointers:
1)pass values by refrence to a function
2)return multiple values from a function
3)use pointers in combinational with arrays
4)dynamic memory allocation
5)use pointers in a base class in order to access object of derived class (Smart pointers)

c++ define function pointer

// Here's a macro I use to define a type.
// You're welcome to use it, but I'll also show how the type is defined.
#define d_typedef_func_ty(return_z, name, ...) typedef return_z (*name)(__VA_ARGS__);
d_typedef_func_ty(int, int_2i_f, int, int); // creates a int(*)(int, int) function pointer
// which is equivelant to the following:
typedef int(*int_2i_f)(int, int);

pointer to pointer c++

#include <iostream>
using namespace std;

struct Distance {
    int feet;
    float inch;
};

int main() {
    Distance *ptr, d;

    ptr = &d;
    
    cout << "Enter feet: ";
    cin >> (*ptr).feet;
    cout << "Enter inch: ";
    cin >> (*ptr).inch;
 
    cout << "Displaying information." << endl;
    cout << "Distance = " << (*ptr).feet << " feet " << (*ptr).inch << " inches";

    return 0;
}

how a function gives a pointer as parameter c++

//example that uses pointer as parameter

// function definition to swap the values.
void swap(int *x, int *y) {
   int temp;
   temp = *x; /* save the value at address x */
   *x = *y; /* put y into x */
   *y = temp; /* put x into y */
  
   return;
}