I’ll adjust the placeholder. As far as the reference to two run functions, I initially named run and evolve the same thing, I must have missed that reference. Most of the stuff in regards to passing hyperparameters via opts is necessary for playing with some configurations later on. For example, opts is used to specify :population_size in initialize. I believe there’s a mistake in the transcription of the signature of initialize where it says:

def initialize(opts \\ []) do
   # ...omitted...
end

It should say:

def initialize(genotype, opts \\ []) do
   # ...omitted...
end

Thank you for the feedback !

I am really enjoying the book (B2) so far.

The version of evolve/4 on page 27 takes genotype as an argument, but it doesn’t seem to need it for anything other than to pass it to itself again recursively. The version on page 28 looks like it was corrected in this regard.

If that isn’t needed, it seems like a slightly prettier way to write run/3 would be:

def run(genotype, fitness_function, max_fitness) do
  genotype
  |> initialize() # maybe call this `initialize_population`
  |> evolve(fitness_function, max_fitness)
end

An even more pedantic suggestion - use verbs for all the function names in the pipeline, i.e., mutate instead of mutation and maybe cross instead of crossover.