@rnd_normal(μ:float, σ:float)
returns a random generator that produces floating-point values according to a normal distribution P:
P(x | μ, σ) = 1/(σ \sqrt{2 π}) e^{- (x - μ)^2/(2 σ^2)}
See @rnd_bernoulli for a description of random generators.
See also Random Generators @rand @rand_int @random @rnd_bernoulli @rnd_binomial @rnd_exponential @rnd_gamma @rnd_geometric @rnd_normal @rnd_uniform_float @rnd_uniform_int