44 lines
1.1 KiB
Ada
44 lines
1.1 KiB
Ada
--
|
|
-- Project Euler problem #7
|
|
--
|
|
-- By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see
|
|
-- that the 6th prime is 13.
|
|
--
|
|
-- What is the 10001st prime number?
|
|
--
|
|
|
|
with Ada.Numerics.Elementary_Functions,
|
|
Ada.Text_IO;
|
|
|
|
use Ada.Numerics.Elementary_Functions,
|
|
Ada.Text_IO;
|
|
|
|
procedure Seven is
|
|
|
|
function Is_Prime (Input : in Natural) return Boolean is
|
|
-- Using the "Trial Division" method detailed in this Wikipedia entry:
|
|
-- https://secure.wikimedia.org/wikipedia/en/wiki/Prime_number#Trial_division
|
|
Ceiling : constant Natural := Natural (Sqrt (Float (Input)));
|
|
begin
|
|
for Index in 2 .. Ceiling loop
|
|
if (Input mod Index) = 0 then
|
|
return false;
|
|
end if;
|
|
end loop;
|
|
return true;
|
|
end Is_Prime;
|
|
|
|
Count : Natural := 0;
|
|
begin
|
|
for N in 2 .. Natural'Last loop
|
|
if Is_Prime (N) then
|
|
Count := (Count + 1);
|
|
|
|
if Count = 10_001 then
|
|
Put_Line (Natural'Image (N) & " is prime");
|
|
return;
|
|
end if;
|
|
end if;
|
|
end loop;
|
|
end Seven;
|