C++ Smart Unique Pointer with polymorphic classes

Introduction

We can utilize polymorphic classes using a unique pointer: 

#include <iostream> 
#include <memory> 

class MyBaseClass 
{ 
public: /*  w  ww .  j  a va 2 s  .  c o  m*/
    virtual void printmessage() 
    { 
        std::cout << "Hello from a base class."; 
    } 
}; 

class MyderivedClass: public MyBaseClass 
{ 
public: 
    void printmessage() 
    { 
        std::cout << "Hello from a derived class."; 
    } 
}; 

int main() 
{ 
    std::unique_ptr<MyBaseClass> p = std::make_unique<MyderivedClass>(); 
    p->printmessage(); 
}

No need to explicitly delete the allocated memory, the smart pointer does it for us.

for calculating the time in seconds it takes to fall a given distance in feet: 

time = sqrt(2 * distance / g)

g is the gravitational constant equal to 32.2 ft/sec2. 

#include <iostream>
#include <cmath>
using namespace std;
int main()//from w  w  w .  j av a  2 s .c om
{
   int height;
   double time;
   height = 800;
   time = sqrt(2 * height / 32.2);
   cout << "It will take " << time << " seconds to fall " << height << " feet.\n";
   return 0;
}



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