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1 perry 1 RANDOM
2 !!!RANDOM
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 RETURN VALUE
7 ERRORS
8 NOTES
9 CONFORMING TO
10 SEE ALSO
11 ----
12 !!NAME
13
14
15 random, srandom, initstate, setstate - random number generator.
16 !!SYNOPSIS
17
18
19 __#include
20 __ ''seed''__);
21 char *initstate(unsigned int__ ''seed''__, char *__''state''__, size_t__ ''n''__);
22 char *setstate(char *__''state''__);
23 __
24 !!DESCRIPTION
25
26
27 The __random()__ function uses a non-linear additive
28 feedback random number generator employing a default table
29 of size 31 long integers to return successive pseudo-random
30 numbers in the range from 0 to __RAND_MAX__. The period
31 of this random number generator is very large, approximately
32 16*((2**31)-1).
33
34
35 The __srandom()__ function sets its argument as the seed
36 for a new sequence of pseudo-random integers to be returned
37 by __random()__. These sequences are repeatable by
38 calling __srandom()__ with the same seed value. If no
39 seed value is provided, the __random()__ function is
40 automatically seeded with a value of 1.
41
42
43 The __initstate()__ function allows a state array
44 ''state'' to be initialized for use by __random()__.
45 The size of the state array ''n'' is used by
46 __initstate()__ to decide how sophisticated a random
47 number generator it should use -- the larger the state
48 array, the better the random numbers will be. ''seed'' is
49 the seed for the initialization, which specifies a starting
50 point for the random number sequence, and provides for
51 restarting at the same point.
52
53
54 The __setstate()__ function changes the state array used
55 by the __random()__ function. The state array
56 ''state'' is used for random number generation until the
57 next call to __initstate()__ or __setstate()__.
58 ''state'' must first have been initialized using
59 __initstate()__ or be the result of a previous call of
60 __setstate()__.
61 !!RETURN VALUE
62
63
64 The __random()__ function returns a value between 0 and
65 RAND_MAX. The __srandom()__ function returns no value.
66 The __initstate()__ and __setstate()__ functions
67 return a pointer to the previous state array, or NULL on
68 error.
69 !!ERRORS
70
71
72 __EINVAL__
73
74
75 A state array of less than 8 bytes was specified to
76 __initstate()__.
77 !!NOTES
78
79
80 Current
81 n'' are 8, 32, 64, 128, and 256 bytes; other
82 amounts will be rounded down to the nearest known amount.
83 Using less than 8 bytes will cause an error.
84 !!CONFORMING TO
85
86
87 BSD 4.3
88 !!SEE ALSO
89
90
91 rand(3), srand(3) [random(3)], [random(4)], [srandom(3)] and [urandom(4)]
92 ----
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