-- Zeitbetrachtungen verschiedener Fibonacci-Implementierungen

with Ada.Calendar,Ada.Integer_text_IO,Ada.text_IO;
use Ada.Calendar,Ada.Integer_text_IO,Ada.text_IO;

with Ada.Numerics.Generic_Elementary_Functions;

procedure fibo is

pragma Optimize(Time);

	--------------------
	-- User-Interface --
	--------------------

	function frage_user return Positive is
		N : Positive;
	begin
		Put("N for Fibonacci (i.e. 30) : ");
		Get(N);
		New_Line;
		return N;
	end frage_user;

	--------------
	-- rek_fibo --
	--------------
	function rek_fibo(zahl : in Positive) return Positive
	-- this is old-style standard recursion --
	is
	begin
	  if (zahl < 3) then
		return 1;
	  else
		return rek_fibo(zahl-1) + rek_fibo(zahl-2);
	  end if;
	end rek_fibo;

	---------------
	-- Iteration --
	---------------

	function it_fibo(wert : in Positive) return Positive
	is
		n1 : Positive := 1;
		n2 : Positive := 1;
		result : Positive;
	begin
	 if (wert < 3) then
	  return 1;
	 else
	   for I in 1 .. wert-2 loop
		result := n1 + n2;
		n1 := n2;
		n2 := result;
           end loop;
           return result;
	 end if;
	end it_fibo;

	-------------
	-- ma_fibo --
	-------------

	function ma_fibo(wert : in Positive) return Positive
	is
		wurzel : constant float := 2.23606797749978969640;
		result : Float;
	begin
		result := (1.0/wurzel)*((((1.0+wurzel)/2.0)**wert)-
			                (((1.0-wurzel)/2.0)**wert));
		return Integer(result);
	end ma_fibo;

	--------------
	-- mak_fibo --
	--------------

	function mak_fibo(wert : in Positive) return Positive
	is
		wurzel : constant float := 2.23606797749978969640;
		bruch : constant float := 1.0 / wurzel;
		plusw : constant float := (1.0 + wurzel)/2.0;
		minusw: constant float := (1.0 - wurzel)/2.0;
		result : Float;
	begin
		result := bruch*(plusw**wert-minusw**wert);
		return Integer(result);
	end mak_fibo;

        --------------
        -- ma2_fibo --
        --------------

        function ma2_fibo(wert : in Positive) return Positive
        is
                wurzel : constant float := 2.23606797749978969640;
                result : Float;
        begin
                result := (1.0/wurzel)*(((1.0+wurzel)**wert-(1.0-wurzel)**wert)/2.0**wert);
                return Integer(result);
        end ma2_fibo;

	------------
	-- report --
	------------

	procedure report (what : in string; dauer : in duration;
			  wert : in Positive; result : in Positive) is
	begin
          Put_Line(what & " for " & Positive'Image(wert) &
		 ": Result: " & Positive'Image(result) &
		 " Duration: " &Duration'Image(dauer) & "s");
	end report;

	----------
	-- Main --
	----------

	startzeit,endzeit : Time;
	dauer : Duration;
	fibowert : Positive;
	result : Positive;
          package mymath is new Ada.Numerics.Generic_Elementary_Functions(Float);
	  use mymath;

begin


	fibowert := frage_user;
	Put_Line("Will do Fibonacci for" & Positive'Image(fibowert));

	startzeit := Clock;
	result := rek_fibo(fibowert);
	endzeit := Clock;
	dauer := endzeit - startzeit;
	report("Standard recursion",dauer,fibowert,result);

	startzeit := Clock;
	result := ma_fibo(fibowert);
	endzeit := Clock;
	dauer := endzeit - startzeit;
	report("Mathematics       ",dauer,fibowert,result);

        startzeit := Clock;
        result := ma2_fibo(fibowert);
        endzeit := Clock;
        dauer := endzeit - startzeit;
        report("Optimized Maths   ",dauer,fibowert,result);

        startzeit := Clock;
        result := mak_fibo(fibowert);
        endzeit := Clock;
        dauer := endzeit - startzeit;
        report("Fixed-term Maths  ",dauer,fibowert,result);

        startzeit := Clock;
        result := it_fibo(fibowert);
        endzeit := Clock;
        dauer := endzeit - startzeit;
        report("Iteration         ",dauer,fibowert,result);

end fibo;