target$ = "METHINKS IT IS LIKE A WEASEL"
      parent$ = "IU RFSGJABGOLYWF XSMFXNIABKT"
      mutation_rate = 0.5
      children% = 10

      DIM child$(children%)

      REPEAT
        bestfitness = 0
        bestindex% = 0
        FOR index% = 1 TO children%
          child$(index%) = FNmutate(parent$, mutation_rate)
          fitness = FNfitness(target$, child$(index%))
          IF fitness > bestfitness THEN
            bestfitness = fitness
            bestindex% = index%
          ENDIF
        NEXT index%

        parent$ = child$(bestindex%)
        PRINT parent$
      UNTIL parent$ = target$
      END

      DEF FNfitness(text$, ref$)
      LOCAL I%, F%
      FOR I% = 1 TO LEN(text$)
        IF MID$(text$, I%, 1) = MID$(ref$, I%, 1) THEN F% += 1
      NEXT
      = F% / LEN(text$)

      DEF FNmutate(text$, rate)
      LOCAL C%
      IF rate > RND(1) THEN
        C% = 63+RND(27)
        IF C% = 64 C% = 32
        MID$(text$, RND(LEN(text$)), 1) = CHR$(C%)
      ENDIF
      = text$