A question about C++ random generator and unsigned method

**joenching** · 03-14-2005

My teacher gave me those code from random.cpp
But i have a question about how to code a Random() constructor in random.h

also, i feel really confuse how to code a Random( unsigned int newSeed ) in random.h too

and what does the "unsigned" for?

Thanks for help me, i would really appericate it.

Code:

// System Include Files
#include <cstdlib>     // Required for RAND_MAX
#include <iostream>

// User Include Files
#include "random.h"

// Namespaces
using namespace std;

// Other Preprocessor Commands
// User Defined Types
// Function Prototypes
// Global Variables - Don't Use!


int main( void )
{
    Random rand;

    int iCtr;

    cout << "Generate 25 random numbers between 0 and 99..." << endl;
    for ( iCtr = 0; iCtr < 25; iCtr++ )
    {
        cout.width( 3 );
        cout << rand.getRandomNumber( 0, 99 ) << " ";
    }
    cout << endl << endl << endl;

    cout << "Generate 15 random numbers between 57 and 189..." << endl;
    for ( iCtr = 0; iCtr < 15; iCtr++ )
    {
        cout.width( 4 );
        cout << rand.getRandomNumber( 57, 189 ) << " ";
    }
    cout << endl << endl;

    unsigned int randNo;

    cout << "Testing 10000 random numbers between 5 and 156..." << endl;
    for ( iCtr = 0; iCtr < 10000; iCtr++ )
    {
        randNo = rand.getRandomNumber( 5, 156 );
        if ( ( randNo < 5 ) || ( randNo > 156 ) )
        {
            cerr << "ERROR: " << randNo << endl;
        }

        if ( ( randNo == 5 ) || ( randNo == 156 ) )
        {
            cout << "Boundry: " << randNo << endl;
        }
    }

    return EXIT_SUCCESS;
}


// End of file: RANDOMTEST.CPP

**hk_mp5kpdw** · 03-14-2005

Your default constructor for the random class should simply call srand using the return value from the time function as input. Your other constructor, the one that takes an unsigned int as an argument, should also call srand but it should pass the unsigned int argument to srand instead of srand initializing itself via the time call. I'm guessing that is what would be required.

Integer and character data types can be either signed or unsigned. A signed int can have values from (assuming 32-bit integers) -2,147,483,648 up to +2,147,483,647. An unsigned int does away with caring about negative values and deals only with the positive meaning that it can hold values from 0 up to +4,294,967,295. By default, if you don't specify signed or unsigned, the compiler will assume signed:

Code:

int val;           // Signed integer value
signed int val;    // Same as above, signed integer value
unsigned int val;  // Unsigned integer value;

**joenching** · 03-14-2005

thanks

can you give me some examples how to what i should type inside the random constructor?

**hk_mp5kpdw** · 03-14-2005

The FAQ has examples of initializing srand using the time function.

**joenching** · 03-14-2005

can you show me how to call a srand and how to return time in random constructor?

**swoopy** · 03-14-2005

>can you show me how to call a srand and how to return time in random constructor?
You don't need to return anything, just call it. This will seed the random number generator.

**joenching** · 03-14-2005

so This is what i did in my random.h file

Code:

#ifndef RANDOM_H
#define RANDOM_H
#include <cstdlib>

class Random
{
public:
	Random()
	{
		int i;
		srand(time(NULL));
	}

is it like that?
However i need to create one more constructor for Random( unsigned int newSeed)

What should i type inside this constructor??

**hk_mp5kpdw** · 03-14-2005

Originally Posted by joenching

so This is what i did in my random.h file

Code:

#ifndef RANDOM_H
#define RANDOM_H
#include <cstdlib>

class Random
{
public:
    Random()
    {
        int i;
        srand(time(NULL));
    }

is it like that?

The part in red above is unnecessary, but other than that, yes.

Originally Posted by joenching

However i need to create one more constructor for Random( unsigned int newSeed)

What should i type inside this constructor??

Originally Posted by me

Your other constructor, the one that takes an unsigned int as an argument, should also call srand but it should pass the unsigned int argument to srand instead of srand initializing itself via the time call.

**joenching** · 03-14-2005

is it like that? the second constactor?

Code:

Random( unsigned int newSeed)
	{
		srand(newSeed);	
	}

Also I have one question about the accessors
I am required to code a function "unsigned int getSeed() const" inside the public

But what should i type for the return type?

[code]
unsigned int getSeed()
{ return ??; }
[code/]

And Do i need to create an attribute inside private?

thanks

**hk_mp5kpdw** · 03-14-2005

Originally Posted by joenching

is it like that? the second constactor?

Code:

Random( unsigned int newSeed)
	{
		srand(newSeed);	
	}

Looks good to me!

**joenching** · 03-14-2005

Also I have one question about the accessors
I am required to code a function "unsigned int getSeed() const" inside the public

But what should i type for the return type?

Code:

unsigned int getSeed()
{ return ??; }

And Do i need to create an attribute inside private?

thanks

**swoopy** · 03-14-2005

It depends on what getSeed() is supposed to do. If it's supposed to automatically generate a seed, then you could call time.

Code:

unsigned int getSeed()
{ return time(NULL); }

If it's supposed to ask the user for a seed, then you could use cin to get input from the user, then return that input as the seed.

>And Do i need to create an attribute inside private?
I don't think so, but I may be misinterpreting what getSeed() does.

**joenching** · 03-14-2005

Hey, this is my header file Randon.h

Code:

#ifndef RANDOM_H
#define RANDOM_H
#include <cstdlib>
#include <ctime>
class Random
{
public:
	Random()
	{
		srand(time(NULL));
	}

	Random( unsigned int newSeed)
	{
		srand(newSeed);	
	}
		
	
	int getRandomNumber( int min = 0, 
						 int max = RAND_MAX ) const
	{
		return time(NULL);
	}
	
		
		
//	bool operator==(const Random& rhRandom) const

//	bool operator!=(const Random& rhRandom) const

//	unsigned int getRandomNumber( unsigned min = 0,
//								  unsigned max = RAND_MAX ) const

//	unsigned int getSeed() const

//	void setSeed( unsigned int newSeed)
//	{
//		number = newSeed;
//	}

private:

	int number;

};

#endif

and this is my cpp file for Random.cpp

Code:

int main( void )
{
    Random rand;

    int iCtr;

    cout << "Generate 25 random numbers between 0 and 99..." << endl;
    for ( iCtr = 0; iCtr < 25; iCtr++ )
    {
        cout.width( 3 );
        cout << rand.getRandomNumber( 0, 99 ) << " ";
    }
    cout << endl << endl << endl;

    cout << "Generate 15 random numbers between 57 and 189..." << endl;
    for ( iCtr = 0; iCtr < 15; iCtr++ )
    {
        cout.width( 4 );
        cout << rand.getRandomNumber( 57, 189 ) << " ";
    }
    cout << endl << endl;

I tried to compile it, it works.. However it shows me a terrible result is like that..

Generate 25 random numbers between 0 and 99...
1110836425 1110836425 1110836425 1110836425 1110836425 1110836425 1110836425 111
0836425 1110836425 1110836425 1110836425 1110836425 1110836425 1110836425 111083
6425 1110836425 1110836425 1110836425 1110836425 1110836425 1110836425 111083642
5 1110836425 1110836425 1110836425

Generate 15 random numbers between 57 and 189...
1110836425 1110836425 1110836425 1110836425 1110836425 1110836425 1110836425 111
0836425 1110836425 1110836425 1110836425 1110836425 1110836425 1110836425 111083
6425

Press any key to continue

Do you know what's wrong is it??

**swoopy** · 03-14-2005

getRandomNumber() should call rand() to get a random number.

By the way, judging from your code, getSeed() would probably look like this instead of what I posted above:

Code:

unsigned int getSeed()
{ return number; }

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