Thread: Another simple program

Hi,

@whiteflags: I can see your point. Not so random then is it in that situation.

However, I'm not entirely sure I understand what rand()%5 actually means, or does. Modulus in my understanding is a number divided into another number, leaving a remainder, so you could check whether a number is even by dividing by 2 (which would leave no remainder).

What would be the min and max values rand()%5 would return?

I think maybe your point is affirmed here:

What is modulus and how do I use it?

with this quote:

"Using % for generating random numbers in a given range is good for quick-and-dirty programming, but it is not particularly good if you need 'industrial strength' pseudo random number generation -- you'll often end up with a skewed distribution.

Edd"

Sam.

This seems to work better for me:

Code:

#include <iostream>
#include <cstdlib>

using namespace std;

int main ()
{
    int numA = 5;
    int numB = 5;
    int answer = numA + numB;
    int guess = 0;
    
    for ( int attempts = 1; attempts<=3 && guess !=answer ; attempts++ )
    {
    cout << "What is " << numA << " + " << numB << "? ";
    cin >> guess;
        
    if (guess == answer)
        {
        cout << "Well done, got it in: " << attempts << " attempts!\n";
        }
        else
        {
            if ( attempts < 3 )
            { 
            cout << "Incorrect. Please try again.\n";
            }
            else
            {
            cout << "Sorry, run out of attempts! Game over...";
            }
        }
    }
}

Got rid of the breaks and seems to function ok.

Still not quite got my head around how to get a random number between 1 and 10 other than rand()%10 which in a lot of forums is not really a good way to do this.

Also, wanted to add a check whether a number has actually been entered, and also to give the user another go with y/n after they get it right.

Sam.

Originally Posted by samwillc

Still not quite got my head around how to get a random number between 1 and 10 other than rand()%10 which in a lot of forums is not really a good way to do this.

Suppose you have a ten sided fair die (numbered 0 to 9), and you want to use it to choose between McDonald's, Chinese food and Turkish food. So, you roll the die, divide the result by 3 and take the remainder. If you get 0, you eat at McDonald's, if you get 1, you eat Chinese food and if you get 2 you eat Turkish food. The thing is, the 10 possible die roll outcomes don't map evenly into the 3 choices, so you are more likely to eat at McDonald's. One way to deal with this is to re-roll if you roll a 9.

Anyway, the latest version of the C++ standard library comes with random number facilities that abstract away this problem.

Your indentation is inconsistent again. Good idea to fix it.
rand() % 11 gives you a number between 0 ... 10. The whole idea is that you are using modulus, which takes the remainder of the number.
0 % 11 == 0
1 % 11 == 1
...
10 % 11 == 10
11 % 11 == 0
12 % 11 == 1
...
etc

For error checking, you do something like

Code:

if (!std::cin)
{
	std::cin.ignore(numeric_limits<streamsize>::max(), '\n');
	std::cin.clear();
}

The first line checks if the input stream is in an inconsistent state, which happens if the user tries to input something that cannot be converted that whatever you are trying to extract.
The next line flushes out the invalid data, and the last one tells the stream that we've taken care of the bad input.

Take a look at, for example: Indent style - Wikipedia, the free encyclopedia