"Ian Abbott" <[EMAIL PROTECTED]> writes:
> On 27 Nov 2001, at 15:16, Hrvoje Niksic wrote:
>
>> So, does anyone know about the portability of rand()?
>
> It's in the ANSI/ISO C spec (ISO 9899). It's always been in UNIX
> (or at least it's been in there since UNIX 7th Edition), and I
> should think it's always been in the MS-DOS compilers, but I don't
> have one handy at the moment.
I've now switched to using it. If someone complains we can resurrect
the check and the dummy implementations. The draft of ISO 9899 I have
even contains such an implementation:
static unsigned long int next = 1;
int rand(void) // RAND_MAX assumed to be 32767
{
next = next * 1103515245 + 12345;
return (unsigned int)(next/65536) % 32768;
}
void srand(unsigned int seed)
{
next = seed;
}
> It tends not to be very random in some implementations, but should
> be good enough to implement a random wait.
Agreed. Besides, I'm using the technique recommended in _Numerical
Recipes in C_, as quoted in the Linux rand(3) man page:
"If you want to generate a random integer between 1 and 10, you
should always do it by using high-order bits, as in
j=1+(int) (10.0*rand()/(RAND_MAX+1.0));
and never by anything resembling
j=1+(rand() % 10);
(which uses lower-order bits)."
