Thread: programming with class

could some one please help me by telling me what is wrong with this program. all i want to do is to display all the asci characters 1-255 using classes because im just learning how to use them

Code:

#include <iostream.h>

class hoha
{
public:
	char current_asci_value=0;
	int index_number =0;

	int displayascivalues(current_asci_value, index_number)
	{
		while(current_asci_value < 255)
		{
			index_number++;
			cout<<current_asci_value;
		}
	}
};

int main()
{
	hoha h;

	h.displayascivalues();
	return 0;
}

You never increment current_asci_value. So you have an infinite loop of the method printing the character equivilent of 0.

-Prelude

You need to assign the value of your ascii char variable inside a constructor or in the main function. When you try to assign it to 0 in the class definition the compiler will think you are trying to declare a pure virtual function. You also need to declare the variable to be int and cast it or you'll get an infinite loop.

Code:

#include <iostream.h>

class hoha
{
  public:
    int current_asci_value;
    hoha()
    {
      current_asci_value = 0;
    }
    void displayascivalues()
    {
      while(current_asci_value < 255) {
        cout<<(char)current_asci_value<<" ";
        current_asci_value++;
      }
    }
};

int main()
{
  hoha h;
  h.displayascivalues();
  return 0;
}

-Prelude

>but what makes it loop forever if you dont cast it
That's one option, the second option is to declare the variable as unsigned char. What is happening is your char wraps around into an infinite loop, it never gets to 254. A signed char only goes to 127 and then wraps around to -128. So, if you declare the variable as int and cast it as a char when you print it you can be sure that it will reach 254. The same goes with an unsigned char which has a range of 0 - 256, it's you're choice which you use.

>and is it nessicery(cant spell) to set the value to 0 in a function
Yes, if you want to set the value then you must either do it in a specific method or the constructor. Another alternative is to pass the value directly to your display method and forgo the class data member.

-Prelude