PROGRAM 1


--  Filename:  prog1a.adb      Author:  Anthony F. Ortiz
--  This program computes and displays the hailstones sequence.
--  rule 1.  start with a postive integer n(1), for i >= 1.
--  rule 2.  if n(i) is even, n(i + 1) = n(i) / 2.
--  rule 3.  if n(1) is odd, n (i + 1) = 3 * n(i) + 1.
--  rule 4.  the sequence terminates with a value of 1.
--  Here is an example 7, 22, 11, 34, 17, 52, 26, 13, 40, 20, 10, 5, 16, 8
--  4, 2, 1.

with Text_IO;  use Text_IO;
procedure Hailstones is
    package Int_IO is new Integer_IO (Integer);  use Int_IO;
    Hailstone:  Integer;  --  Next hailstone.
    Temp     :  Integer;  --  Temporary placement for current hailstone.
begin        
    --  Enter starting hailstone.
    Put ("enter a number from 2 to 500. ");
    Get (Hailstone);
    New_Line;
    --  Loop until hailstone = 1.
    while (Hailstone /= 1) loop
        --  Compute formula 1 if hailstone is odd.  Compute formula 2 if
        --  hailstone is even.  Place the value in temp so the second if
        --  statement doesn't affect hailstone.  After both if statements
        --  execute, put the value in temp into hailstone.
        if ((Hailstone mod 2) = 0) then
            Temp := Hailstone / 2;
        else 
            Temp := 3 * Hailstone + 1;
        end if;
        Hailstone := Temp;
        --  Display next hailstone.
        Put (Hailstone, 10);
    end loop;
end Hailstones;

--  outfile:  prog1a.out

enter a number from 2 to 500. 25

        76        38        19        58        29        88        44        22
        11        34        17        52        26        13        40        20
        10         5        16         8         4         2         1




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