C / Random Value

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AmiDARK

C / Random Value

Posted on: 2009/3/9 21:52 #1

Quite a regular

Hi All,

I've seen that I can use rand() or srand() to generate randoms numbers but I don't understand how I can exactly set a limit to rand value.

For exemple, I want to get a random number between 0 - 640 ...

I can I proceed ?

I tried to create this function :


int Rnd( int RangeValue ){

  float NewRandom = (float)( rand() & 0x7FFFFFFF );

  float NewFACTOR = (float)( RangeValue / 2147483647 ) ; // 2147483647 = 0x7FFFFFFF

  NewRANDOM = NewRANDOM * NewFACTOR;

  return (int)NewRANDOM;

 }

Thank you.

Edited by freddix on 2009/3/9 22:16:16

All we have to decide is what to do with the time that is given to us.

Radov

Re: C / Random Value

Posted on: 2009/3/9 22:58 #2

Just popping in

@freddix

Hi!

All You need is "%" modulo division, ex
int rangedValue = value % range;

AmiDARK

Re: C / Random Value

Posted on: 2009/3/9 23:02 #3

Quite a regular

@Radov
I'm sorry but I don't understand what you mean ...

All we have to decide is what to do with the time that is given to us.

thomas

Re: C / Random Value

Posted on: 2009/3/9 23:04 #4

Not too shy to talk

@freddix

Quote:

For exemple, I want to get a random number between 0 - 640 ...


#define rnd(lo,hi) ((rand() % ((hi) - (lo) + 1)) + (lo))

Bye,
Thomas

yescop

Re: C / Random Value

Posted on: 2009/3/9 23:08 #5

Just popping in

@freddix

Hi,

reading the C manual, you can see that rand returns a pseudo number between 0 and RAND_MAX.

So to have a number between 0 and 640, you can do this :

A = rand();

A = A- 640 * int(A/640) ; // A = A modulo 640.

But I suggest you to use other algorithm like md5.
You will have a better random number generator.

Hope that this can help you.

AmiDARK

Re: C / Random Value

Posted on: 2009/3/9 23:34 #6

Quite a regular

@yescop
Thank you for these informations.

It now work perfectly :)

Regards,
AmiDARK.

All we have to decide is what to do with the time that is given to us.

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