Random Numbers ============== 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. - Variable: *random-state* 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.