@rnd_geometric(p:int)
returns a random generator that produces integers following a geometric discrete distribution:
P(i | p) = p (1 - p)^i, i ≥ 0.
See @rnd_bernoulli for a description of random generators.
See also Random Related Functions @rand, @rand_int, @random, @rnd_bernoulli, @rnd_binomial, @rnd_exponential, @rnd_gamma, @rnd_geometric, @rnd_normal, @rnd_uniform_float, @rnd_uniform_int