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 -- -- Project Euler problem #3 -- -- The prime factors of 13195 are 5, 7, 13 and 29. -- -- What is the largest prime factor of the number 600851475143 ? with Ada.Command_Line, Ada.Containers.Vectors, Ada.Numerics.Elementary_Functions, Ada.Text_IO; use Ada.Containers, Ada.Numerics.Elementary_Functions, Ada.Text_IO; procedure Three is package CL renames Ada.Command_Line; -- For this problem, we need a 64-bit Natural subtype subtype Long_Natural is Long_Integer range 0 .. Long_Integer'Last; package Bucket is new Ada.Containers.Vectors (Index_Type => Natural, Element_Type => Long_Natural); -- Return a Vector with all the factors for `Input` function Factors_For (Input : in Long_Natural) return Bucket.Vector is Result : Bucket.Vector; -- Using the "Trial Division" method detailed in this Wikipedia entry: -- https://secure.wikimedia.org/wikipedia/en/wiki/Prime_number#Trial_division Ceiling : constant Long_Natural := Long_Natural (Sqrt (Float (Input))); begin for Index in 2 .. Ceiling loop if (Input mod Index) = 0 then Bucket.Append (Result, Index); end if; end loop; return Result; end Factors_For; begin if CL.Argument_Count < 1 then Put_Line (">>> Insufficient command line parameters!"); New_Line; Put_Line ("Please execute with: " & CL.Command_Name & " "); CL.Set_Exit_Status (CL.Failure); return; end if; declare Passed_Number : constant Long_Natural := Long_Natural'Value (CL.Argument (1)); Factors : constant Bucket.Vector := Factors_For (Passed_Number); begin Put_Line ("Looking for the largest prime factors for:" & Long_Natural'Image (Passed_Number)); New_Line; for Index in 0 .. Bucket.Last_Index (Factors) loop declare Factor : constant Long_Natural := Bucket.Element (Factors, Index); New_Factors : constant Bucket.Vector := Factors_For (Factor); begin if Bucket.Length (New_Factors) = 0 then Put_Line (Long_Natural'Image (Factor) & " looks like a prime"); end if; end; end loop; end; end Three;
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