Function that returns a random number

Tori · #1 02-Nov-2004, 16:24

I need to write a function called generate that returns a random number between x and y. I have writen the code below, but it will not compile. Any suggestions would be appriciated.

davekw7x · #2 02-Nov-2004, 18:14

Quote:

Originally Posted by Tori

I need to write a function called generate that returns a random number between x and y. I have writen the code below, but it will not compile. Any suggestions would be appriciated.

Look at my response to your other question for hints on getting it to compile. If you have additional questions, post the specific questions with your current code.

Regards,

Dave

WaltP · #3 02-Nov-2004, 21:56

Quote:

Originally Posted by davekw7x

Look at my response to your other question for hints on getting it to compile. If you have additional questions, post the specific questions with your current code.

Regards,

Dave

Also, please post short segments of code in your post, not as an attachment. More people will look at the code this way. I for one don't download attachments -- takes too long, can be dangerous, etc. And be sure to use code tags. "Don't post code without them" as Karl Malden might have said (how many of you remember where that comes from?

)

LuciWiz · #4 03-Nov-2004, 01:27

Quote:

Originally Posted by Tori

I need to write a function called generate that returns a random number between x and y. I have writen the code below, but it will not compile. Any suggestions would be appriciated.

See Dave's answer for solving this problem.
I just want to point out a couple of things in your algorithm. First of all, what I understand from your code, you want to generate a random number between x and y.
However, this line of code will generate a number between x and x + y :

CPP / C++ / C Code:

	return ( x + rand() % (y + 1));

I suggest you use this instead:

CPP / C++ / C Code:

	return ( x + rand() % (y + 1 - x));

Also, if you will run the program several times, you will notice that if you provide the same range values, it will give you the same result! This might not bother you, but in case it does, you could use srand to initialise the random number generator. In order to really make it random, you could use the current time (it will be different next time you run the program!). Be carefull: ony use srand one time in your program, before the call to rand; this is my version of your program

CPP / C++ / C Code:

#include <iostream>
#include <cstdlib>
#include <ctime>
#include "conio.h"


using std::cout;
using std::cin;
using std::endl;

int generate (int, int);

int main()
{
	int x;	// smallest number
	int y;	// largest number
	int z;	// random number

	cout << "Enter smallest number in range\n";
	cin >> x;

	cout << "Enter largest number in range\n";
	cin >> y;

srand(static_cast<unsigned>(time(0)));

	z = generate(x,y);
	cout << "The random number is:" << z << endl;
		
	getch();

   return 0;    // indicate the program ended successfully
}

int generate (int x, int y)
{

return ( x + rand() % (y + 1 - x));

//	return ( x + rand() % (y + 1));

}

Kind regards,
Luci

WaltP · #5 03-Nov-2004, 21:48

Quote:

Originally Posted by LuciWiz

I suggest you use this instead:

CPP / C++ / C Code:

return ( x + rand() % (y + 1 - x));

Nitpick time....

Parentheses will help understanding of this line just a little better:

CPP / C++ / C Code:

return ( x + (rand() % (y + 1 - x)));

Yes, we know the % is done before a +, but not everyone does. And for those that don't quite have a grasp of the operator hierarchy, this will help. Even I have to think about it sometimes...

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