randInt [[<min>] <max>]
This returns a random integer. With no arguments, the number will be either 0 or 1 with equal chance. With one argument, the number will be in the range [0, max). With two arguments, the number will be in the range [min, max).
This uses the same generator that Lens uses for its internal random integers. Therefore, calling this will affect the next value used when selecting examples probabilistically or in other discrete randomized procedures.