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This package also provides an implementation of the Common Lisp random number generator. It uses its own additive-congruential algorithm, which is much more likely to give statistically clean random numbers than the simple generators supplied by many operating systems.
Function: random* number &optional state
This function returns a random nonnegative number less than
number, and of the same type (either integer or floating-point).
The state argument should be a random-state object
which holds the state of the random number generator. The
function modifies this state object as a side effect. If
state is omitted, it defaults to the variable
*random-state*, which contains a pre-initialized
random-state object.
This variable contains the system "default" random-state
object, used for calls to random* that do not specify an
alternative state object. Since any number of programs in the
Emacs process may be accessing *random-state* in interleaved
fashion, the sequence generated from this variable will be
irreproducible for all intents and purposes.
Function: make-random-state &optional state
This function creates or copies a random-state object.
If state is omitted or nil, it returns a new copy of
*random-state*. This is a copy in the sense that future
sequences of calls to (random* n) and
(random* n s) (where s is the new
random-state object) will return identical sequences of random
numbers.
If state is a random-state object, this function
returns a copy of that object. If state is t, this
function returns a new random-state object seeded from the
date and time. As an extension to Common Lisp, state may also
be an integer in which case the new object is seeded from that
integer; each different integer seed will result in a completely
different sequence of random numbers.
It is legal to print a random-state object to a buffer or
file and later read it back with read. If a program wishes
to use a sequence of pseudo-random numbers which can be reproduced
later for debugging, it can call (make-random-state t) to
get a new sequence, then print this sequence to a file. When the
program is later rerun, it can read the original run's random-state
from the file.
Function: random-state-p object
This predicate returns t if object is a
random-state object, or nil otherwise.
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