@rnd_exponential(λ:float)

returns a random generator that produces floats x according to an exponential distribution P of parameter λ:

    P(x | λ) = λ e^(-λ x),    x > 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