Lucas-Lehmer test: Difference between revisions

=={{header|Ada}}==

with Ada.Text_Io; use Ada.Text_Io;

with Ada.Integer_Text_Io; use Ada.Integer_Text_Io;

with Ada.Numerics.Elementary_Functions; use Ada.Numerics.Elementary_Functions;

procedure Lucas_Lehmer_Test is

function Mersenne(Item : Integer) return Boolean is

S : Long_Long_Integer := 4;

MP : Long_Long_Integer := 2**Item - 1;

begin

if Item = 2 then

return True;

else

for I in 3..Item loop

S := (S * S - 2) mod MP;

end loop;

return S = 0;

end if;

end Mersenne;

Upper_Bound : constant Integer := Integer(Float'Rounding(Log(10.0) / Log(2.0) * 10_000_000.0));

M_Count : Natural := 0;

begin

Put_Line(" Mersenne primes:");

for P in 2..Upper_Bound loop

if Mersenne(P) then

Put(" M");

Put(Item => P, Width => 1);

M_Count := M_Count + 1;

exit when M_Count = 45;

end if;

end loop;

end Lucas_Lehmer_Test;

Output: (Output was truncated by an arithmetic overflow exception.)

Mersenne primes:

M2 M3 M5 M7 M13 M17 M19 M31