N = 10
      DIM mname$(N), wname$(N), mpref$(N), wpref$(N), mpartner%(N), wpartner%(N)
      DIM proposed&(N,N)
      mname$() = "", "Abe","Bob","Col","Dan","Ed","Fred","Gav","Hal","Ian","Jon"
      wname$() = "", "Abi","Bea","Cath","Dee","Eve","Fay","Gay","Hope","Ivy","Jan"
      mpref$() = "", "AECIJDFBHG","CHADEFBJIG","HEADBFIGCJ","IFDGHEJBCA","JDBCFEAIHG",\
      \              "BADGEICJHF","GEIBCADHJF","AEHFICJBGD","HCDGBAFIJE","AFJGEBDCIH"
      wpref$() = "", "BFJGIADECH","BACFGDIEJH","FBEGHCIADJ","FJCAIHGDBE","JHFDAGCEIB",\
      \              "BAEIJDFGCH","JGHFBACEDI","GJBAIDHECF","ICHGFBAEJD","EHGABJCIFD"

      REM The Gale-Shapley algorithm:
      REPEAT
        FOR m% = 1 TO N
          REPEAT
            IF mpartner%(m%) EXIT REPEAT
            FOR i% = 1 TO N
              w% = ASCMID$(mpref$(m%),i%) - 64
              IF proposed&(m%,w%) = 0 EXIT FOR
            NEXT i%
            IF i% > N EXIT REPEAT
            proposed&(m%,w%) = 1
            IF wpartner%(w%) = 0 THEN
              mpartner%(m%) = w% : REM Get engaged
              wpartner%(w%) = m%
            ELSE
              o% = wpartner%(w%)
              IF INSTR(wpref$(w%), LEFT$(mname$(m%),1)) < \
              \  INSTR(wpref$(w%), LEFT$(mname$(o%),1)) THEN
                mpartner%(o%) = 0  : REM Split up
                mpartner%(m%) = w% : REM Get engaged
                wpartner%(w%) = m%
              ENDIF
            ENDIF
          UNTIL TRUE
        NEXT m%
      UNTIL SUM(mpartner%()) = (N*(N+1))/2

      FOR m% = 1 TO N
        PRINT mname$(m%) " is engaged to " wname$(mpartner%(m%))
      NEXT
      PRINT "Relationships are ";
      IF FNstable PRINT "stable." ELSE PRINT "unstable."

      a% = RND(N)
      REPEAT b% = RND(N) : UNTIL b%<>a%
      PRINT '"Now swapping " mname$(a%) "'s and " mname$(b%) "'s partners:"
      SWAP mpartner%(a%), mpartner%(b%)
      PRINT mname$(a%) " is engaged to " wname$(mpartner%(a%))
      PRINT mname$(b%) " is engaged to " wname$(mpartner%(b%))
      PRINT "Relationships are ";
      IF FNstable PRINT "stable." ELSE PRINT "unstable."
      END

      DEF FNstable
      LOCAL m%, w%, o%, p%
      FOR m% = 1 TO N
        w% = mpartner%(m%)
        FOR o% = 1 TO N
          p% = wpartner%(o%)
          IF INSTR(mpref$(m%), LEFT$(wname$(o%),1)) < \
          \  INSTR(mpref$(m%), LEFT$(wname$(w%),1)) AND \
          \  INSTR(wpref$(o%), LEFT$(mname$(m%),1)) < \
          \  INSTR(wpref$(o%), LEFT$(mname$(p%),1)) THEN
            = FALSE
          ENDIF
        NEXT o%
      NEXT m%
      = TRUE