Return a pseudo-random number.
All integers representable in Lisp, i.e. between `most-negative-fixnum'
and `most-positive-fixnum', inclusive, are equally likely.
With positive integer LIMIT, return random number in interval [0,LIMIT).
With argument t, set the random number seed from the current time and pid.
With a string argument, set the seed based on the string's contents.
Other values of LIMIT are ignored.
See Info node `(elisp)Random Numbers' for more details. (fn &optional LIMIT)