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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.
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 that 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 internal variablecl--random-state
, which contains a pre-initialized defaultrandom-state
object. (Since any number of programs in the Emacs process may be accessingcl--random-state
in interleaved fashion, the sequence generated from this will be irreproducible for all intents and purposes.)
This function creates or copies a
random-state
object. If state is omitted ornil
, it returns a new copy ofcl--random-state
. This is a copy in the sense that future sequences of calls to(cl-random
n)
and(cl-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 ist
, this function returns a newrandom-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 valid to print a
random-state
object to a buffer or file and later read it back withread
. If a program wishes to use a sequence of pseudo-random numbers which can be reproduced later for debugging, it can call(cl-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.