C++ Programming Code Examples
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Virtual function: respond to random events
/* Virtual function: respond to random events */
#include <iostream>
#include <cstdlib>
using namespace std;
class BaseClass {
public:
int i;
BaseClass(int x) {
i = x;
}
virtual void myFunction()
{
cout << "Using BaseClass version of myFunction(): ";
cout << i << '\n';
}
};
class DerivedClass1 : public BaseClass {
public:
DerivedClass1(int x) : BaseClass(x) {}
void myFunction()
{
cout << "Using DerivedClass1's version of myFunction(): ";
cout << i*i << '\n';
}
};
class DerivedClass2 : public BaseClass {
public:
DerivedClass2(int x) : BaseClass(x) {}
void myFunction()
{
cout << "Using DerivedClass2's version of myFunction(): ";
cout << i+i << '\n';
}
};
int main()
{
BaseClass *p;
DerivedClass1 derivedObject1(10);
DerivedClass2 derivedObject2(10);
int i, j;
for(i = 0; i <10; i++) {
j = rand();
if( ( j % 2 ) )
p = &derivedObject1;
else
p = &derivedObject2;
p->myFunction(); // call appropriate function
}
return 0;
}
Consider a situation, when we have two persons with the same name, jhon, in the same class. Whenever we need to differentiate them definitely we would have to use some additional information along with their name, like either the area, if they live in different area or their mother's or father's name, etc. Same situation can arise in your C++ applications. For example, you might be writing some code that has a function called xyz() and there is another library available which is also having same function xyz(). Now the compiler has no way of knowing which version of xyz() function you are referring to within your code.
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Generate random number. Returns a pseudo-random integral number in the range between 0 and RAND_MAX. This number is generated by an algorithm that returns a sequence of apparently non-related numbers each time it is called. This algorithm uses a seed to generate the series, which should be initialized to some distinctive value using function srand. RAND_MAX is a constant defined in <cstdlib>. The rand() function in C++ is used to generate random numbers; it will generate the same number every time we run the program. In order to seed the rand() function, srand(unsigned int seed) is used. The srand() function sets the initial point for generating the pseudo-random numbers. The rand() function generates numbers randomly.
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