forked from KolibriOS/kolibrios
117 lines
2.8 KiB
Plaintext
117 lines
2.8 KiB
Plaintext
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(*
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adapted to Oberon-07 by 0CodErr, KolibriOS team
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*)
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(*
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The Hailstone sequence of numbers can be generated
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from a starting positive integer, n by:
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IF n is 1 THEN the sequence ends.
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IF n is even THEN the next n of the sequence = n / 2
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IF n is odd THEN the next n of the sequence = (3 * n) + 1
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The (unproven) Collatz conjecture is that the hailstone sequence
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for any starting number always terminates.
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*)
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MODULE hailst;
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IMPORT In, Out, API, Console;
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CONST
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maxCard = ROR(-2, 1) DIV 3;
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List = 1;
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Count = 2;
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Max = 3;
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VAR
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a: INTEGER;
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PROCEDURE HALT(code: INTEGER);
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BEGIN
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In.Ln; Console.exit(TRUE); API.exit(code)
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END HALT;
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PROCEDURE HailStone(start, _type: INTEGER): INTEGER;
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VAR
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n, max, count, res: INTEGER;
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exit: BOOLEAN;
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BEGIN
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count := 1;
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n := start;
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max := n;
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exit := FALSE;
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WHILE exit # TRUE DO
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IF _type = List THEN
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Out.Int (n, 12);
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IF count MOD 6 = 0 THEN Out.Ln END
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END;
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IF n # 1 THEN
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IF ODD(n) THEN
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IF n < maxCard THEN
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n := 3 * n + 1;
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IF n > max THEN max := n END
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ELSE
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Out.String("Exceeding max value for type INTEGER at:");
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Out.Ln;
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Out.String("n = "); Out.Int(start, 1);
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Out.String(", count = "); Out.Int(count, 1);
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Out.String(", intermediate value ");
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Out.Int(n, 1);
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Out.String(". Aborting.");
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Out.Ln;
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HALT(2)
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END
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ELSE
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n := n DIV 2
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END;
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INC(count)
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ELSE
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exit := TRUE
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END
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END;
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IF _type = Max THEN res := max ELSE res := count END
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RETURN res
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END HailStone;
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PROCEDURE FindMax(num: INTEGER);
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VAR
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val, maxCount, maxVal, cnt: INTEGER;
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BEGIN
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maxCount := 0;
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maxVal := 0;
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FOR val := 2 TO num DO
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cnt := HailStone(val, Count);
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IF cnt > maxCount THEN
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maxVal := val;
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maxCount := cnt
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END
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END;
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Out.String("Longest sequence below "); Out.Int(num, 1);
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Out.String(" is "); Out.Int(HailStone(maxVal, Count), 1);
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Out.String(" for n = "); Out.Int(maxVal, 1);
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Out.String(" with an intermediate maximum of ");
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Out.Int(HailStone(maxVal, Max), 1);
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Out.Ln
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END FindMax;
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BEGIN
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Console.open;
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a := HailStone(27, List);
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Out.Ln;
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Out.String("Iterations total = "); Out.Int(HailStone(27, Count), 1);
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Out.String(" max value = "); Out.Int(HailStone(27, Max), 1);
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Out.Ln;
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FindMax(100000);
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Out.String("Done.");
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Out.Ln; In.Ln;
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Console.exit(TRUE)
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END hailst.
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