MODULE DammAlgorithm EXPORTS Main;

IMPORT IO, Text;

VAR
  Numbers:ARRAY[0..3] OF TEXT := ARRAY OF TEXT{"5724", "5727", "112946", "112949"};

PROCEDURE Damm(READONLY Str:TEXT):BOOLEAN =
  TYPE
    TTable = ARRAY[0..9],[0..9] OF INTEGER;
  VAR
    Table := TTable
    {ARRAY OF INTEGER{0,3,1,7,5,9,8,6,4,2},
     ARRAY OF INTEGER{7,0,9,2,1,5,4,8,6,3},
     ARRAY OF INTEGER{4,2,0,6,8,7,1,3,5,9},
     ARRAY OF INTEGER{1,7,5,0,9,8,3,4,2,6},
     ARRAY OF INTEGER{6,1,2,3,0,4,5,9,7,8},
     ARRAY OF INTEGER{3,6,7,4,2,0,9,5,8,1},
     ARRAY OF INTEGER{5,8,6,9,7,2,0,1,3,4},
     ARRAY OF INTEGER{8,9,4,5,3,6,2,0,1,7},
     ARRAY OF INTEGER{9,4,3,8,6,1,7,2,0,5},
     ARRAY OF INTEGER{2,5,8,1,4,3,6,7,9,0}};
    Interim,I:INTEGER := 0;
  BEGIN
    WHILE I <= Text.Length(Str)-1 DO
      Interim := Table[Interim, ORD(Text.GetChar(Str, I)) - ORD('0')];
      INC(I);
    END;
    RETURN Interim = 0;
  END Damm;

BEGIN
  FOR I := FIRST(Numbers) TO LAST(Numbers) DO
    IF Damm(Numbers[I]) THEN
      IO.Put(Numbers[I] & " is valid\n");
    ELSE
      IO.Put(Numbers[I] & " is invalid\n");
    END;
  END;
END DammAlgorithm.