(defn crossover
  "Produces a new vector based on the genotypes [gt1 gt2] taking the mask as
  the crossover guide {1 = copy, 0 = not-copy}. The genes from [gt2] are
  copyed to [gt1]."
  [gt1 gt2 mask]
  (let [inv-mask (mapv #(- 1 %) mask)
        masked-gt1 (mapv * gt1 inv-mask)
        masked-gt2 (mapv * gt2 mask)]
    (mapv + masked-gt1 masked-gt2)))