PRINT FNmarkov("ruleset1.txt", "I bought a B of As from T S.")
      PRINT FNmarkov("ruleset2.txt", "I bought a B of As from T S.")
      PRINT FNmarkov("ruleset3.txt", "I bought a B of As W my Bgage from T S.")
      PRINT FNmarkov("ruleset4.txt", "_1111*11111_")
      PRINT FNmarkov("ruleset5.txt", "000000A000000")
      END

      DEF FNmarkov(rulefile$, text$)
      LOCAL i%, done%, rules%, rule$, old$, new$
      rules% = OPENIN(rulefile$)
      IF rules%=0 ERROR 100, "Cannot open rules file"
      REPEAT
        rule$ = GET$#rules%
        IF ASC(rule$)<>35 THEN
          REPEAT
            i% = INSTR(rule$, CHR$(9))
            IF i% MID$(rule$,i%,1) = " "
          UNTIL i%=0
          i% = INSTR(rule$, " -> ")
          IF i% THEN
            old$ = LEFT$(rule$,i%-1)
            WHILE RIGHT$(old$)=" " old$ = LEFT$(old$) : ENDWHILE
            new$ = MID$(rule$,i%+4)
            WHILE ASC(new$)=32 new$ = MID$(new$,2) : ENDWHILE
            IF ASC(new$)=46 new$ = MID$(new$,2) : done% = TRUE
            i% = INSTR(text$,old$)
            IF i% THEN
              text$ = LEFT$(text$,i%-1) + new$ + MID$(text$,i%+LEN(old$))
              PTR#rules% = 0
            ENDIF
          ENDIF
        ENDIF
      UNTIL EOF#rules% OR done%
      CLOSE #rules%
      = text$