dev-cpp-users

[Dev-C++] how to use "srand"

[swagat k. <sw...@ma...>]

Hi!
friends...i have got a doubt...

how to use srand() function. how to define the seed for this.
suppose i want to generate a random number between 0 and 10. then what seed should i use...

though rand() function works fine....i just wanted to know the difference beween srand() and rand()...






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RE: [Dev-C++] how to use "srand"

[Ioannis V. <iv...@em...>]

> -----Original Message-----
> From: dev...@li... 
> [mailto:dev...@li...] On Behalf 
> Of swagat kumar
> Sent: Thursday, March 20, 2003 10:10 AM
> To: dev...@li...
> Subject: [Dev-C++] how to use "srand"
> 
> 
> Hi!
> friends...i have got a doubt...
> 
> how to use srand() function. how to define the seed for this.
> suppose i want to generate a random number between 0 and 10. 
> then what seed should i use...
> 
> though rand() function works fine....i just wanted to know 
> the difference beween srand() and rand()...


Rand() defines a pseudo-random sequence. Srand() defines the starting point
based on a seed. So if you do not srand(), or srand() the same number you
will always getting the same sequence.


So, better do that:

/* C */

#include <stdlib.h>
#include <time.h>

/* ... */

int x;

/* initialize only once */
srand(time(NULL));


x=rand();

/* ... */

x=rand();

/* etc */



Ioannis Vranos
 
* Programming pages: http://www.noicys.freeurl.com
* Alternative URL: http://run.to/noicys

Re: [Dev-C++] how to use "srand"

[Richard C. <tel...@ya...>]

thing with random numbers is, the same input put into the same processes will only every generate the same "random" numbers, hence the term pseudo-
random.

it was always my understanding that srand() had to be called before rand() but apparently that's not the case... *shrug* but from ioannis it seems 
rand() must have a default seed it runs off.

but most random number classes require a seed, just as a starting point. if this seed is the same, then the random numbers will be the same. but 
using the system time is a pretty good way to mix up your numbers a bit.