[C++] Random Numbers help

[alexz003]

Hello, i am currently making a text RPG but for specific monsters i want their damage to be withing a certain range of number and then choose them randomly. Please help

 

[Negata]

It's usually (afaik) done by using modulus (% -operator).
For example: your_random_number % 500 would give a number in the 0-499 range.

 

[alexz003]

what if i want it between like 13 and 20?

 

[BBim]

what if i want it between like 13 and 20?

Google on how to get a random number, then take using what you found, a random number that goes from 0 to MAX - MIN, then make the result plus MIN.
from 13 to 20 would be a number from 0 to 7(or 8 if the last number is not include, I dont remember)
if the result is 0, plus 13 = 13(min)
if it is 7, plus 13 = 20(max).

You can also use an algorithm like MersenneTwister, google for that also.

 

[alexz003]

im sorry im so confused with what you said BBim im just looking for something similar to

rand(min, max);

 

[Team Lion]

(rand() * (High - Low - 1)) + Low;
Generates a random number between [Low, High) (e.x from Low <= number < High)

That or using modulo is really the only two ways I've ever seen it done.

 

[alexz003]

can you explain modulo please?

 

[Daevius]

Modulo divides A by B and returns the rest:

5 % 2 = 1 (because 5 / 2 = 2.5, rest is 0.5 * 2 = 1).
9 % 5 = 4

So, if you get a random number, you first limit it's range (and still keep it random) by using the modulo operation. Then you can add or subtract to the whole range to move it around. Pretty straightforward.

#include <iostream>
#include <cstdlib>

int main()
{
    unsigned int max = 500, min = 100;

    if ((max - min) > RAND_MAX)
    {
        std::cerr << "Range overflows the maximum of rand();\n";
    }

    while (1)
    {
        unsigned int random = (rand() % ((max - min) + 1))) + min;
        std::cout << random << '\n';
    }
    //return 0;
}

 

[alexz003]

I tried using your example Team Lion and when i put it in like this

case 1:
                                   cout << "The walking Mushroom attacks!\n";
                                   unsigned int  UHP - (rand() * (8 - 2 - 1)) + 2;
                                   cout << "You now have " << UHP << " Health Points left!\n";
                                   system("pause");

It won't change

 

[Daevius]

Why don't you get a compile error, the minus ( - ) behind UHP when trying to define it should be an is ( = ).

Also, it is advised to use brackets for case statements.

 

[alexz003]

I do use case statements. i didn't get a error because it is a valid operation. and i still need information on the question at hand.

 

[Negata]

You seem to lack a lot on very basics of c++. I greatly advice reading a book or something because most of your questions lately fail because of very simple mistakes that aren't related to the actual problem.

 

[alexz003]

Then how come i have yet to see you fix my problems? The only stuff you put on here are things that are not answering my question.

 

[Daevius]

We're trying to help you, not just answering your exact questions, we aren't slaves.

Now figure it out yourself, you've got your random-number questions answered.