Array#ractor_map

ractor_map.rb

using Module.new {
  refine(Array) do
    def ractor_map(&block)
      rs = map.with_index do |x, index|
        r = Ractor.new(x, &block)
        Ractor.new(r, index) do |r, index|
          [r.take, index]
        end
      end
      result = []
      until rs.empty?
        r, ret = Ractor.select(*rs)
        rs.delete(r)
        result[ret[1]] = ret[0]
      end
      result
    end
  end
}

ns = 10.times.to_a

p ns.map { sleep 1; _1 * _1 }
p ns.ractor_map { sleep 1; _1 * _1 }

Here is the same but for async: https://github.com/socketry/async-await/blob/master/lib/async/await/enumerable.rb