ok@quintus (11/27/88)
The SunOS 3.2 on-line manual page for rand(3v) says:
rand uses a multiplicative congruential random number gen-
erator with period 2**32 to return successive pseudo-random
numbers in the range from 0 to (2**15)-1.
In fact it generates 31-bit integers, as the following test program shows:
main()
{
extern int rand();
extern void srand();
int i;
srand(21345);
for (i = 1; i <= 20; i++) printf("%12d\n", rand());
}
--
This program generates identical results on a Sun-3/60 and a Sequent 386.
The Sequent documentation describes the range correctly.
The SVID specifies 15-bit results. The BSD/SV incompatibility is known, but
it looked as though SunOS 3.2 had adopted the SV definition. Nope, you still
need (rand()&32767) for portability.guy@auspex.UUCP (Guy Harris) (11/29/88)
>The SVID specifies 15-bit results. The BSD/SV incompatibility is >known, Actually, as I remember it's a 32V/SV incompatibility; another BSD/S5 difference that was originally an AT&T/AT&T difference.... >but it looked as though SunOS 3.2 had adopted the SV definition. Which wouldn't have been a good idea, for compatibility reasons. The real story is that the "rand" in the 4BSD environment and the "rand" in the S5 environment differ; at least in 4.0, the former is described in RAND(3C) and the latter is described in RAND(3V). This may be the case in 3.x as well; "man" has the annoying habit of choosing the 3V page rather than the 3C page if you don't give a section, so "man rand" gives the S5-environment version.
ok@quintus.uucp (Richard A. O'Keefe) (11/29/88)
In article <527@auspex.UUCP> guy@auspex.UUCP (Guy Harris) writes: >This may be the case >in 3.x as well; "man" has the annoying habit of choosing the 3V page >rather than the 3C page if you don't give a section, so "man rand" gives >the S5-environment version. AAARGH! That's IT! "man 3c rand" gives me the BSD man page. This would be reasonable behaviour for "man" if I had /usr/5bin early in my $PATH, but I haven't got it in my $PATH _at_all_. Ok, let's count _that_ as the bug.