random: pseudorandom number generator
value init : int > unit

Initialize the generator, using the argument as a seed.
The same seed will always yield the same sequence of numbers.
value full_init : int vect > unit

Same as init but takes more data as seed. It is not
useful to give more than 55 integers.
value int : int > int

random__int bound returns a random number between 0 (inclusive)
and bound (exclusive). bound must be positive and smaller
than 2^{30}.
value float : float > float

random__float bound returns a random number between 0 (inclusive)
and bound (exclusive).