unit Opgave4A;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Label4: TLabel;
    Label5: TLabel;
    Label6: TLabel;
    Label7: TLabel;
    Label8: TLabel;
    Label9: TLabel;
    Bereken: TButton;
    Wis: TButton;
    Deelintervallen: TEdit;
    Bovengr: TEdit;
    Ondergr: TEdit;
    Resultaat: TMemo;
    memFout: TMemo;

    procedure WisClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure BerekenClick(Sender: TObject);


  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  ondergrens, bovengrens, deelinterval, Fx, Fboven, Fonder, Fnum, Fout, FoutMax: Real;
  stap, i: integer;
  x_rij: array of Real;
  FIarr: array of Real;
  Farr: array of Real;
  FnumIarr: array of Real;

implementation

{$R *.dfm}


function FI(x: real):real;
begin
  FI := (0.25 * x*x*x*x) - ((5/3) * x*x*x) + (x*x) + 3 * x;
end;

function F(x: real):real;
begin
  F := (x*x*x) - 5 *(x*x) + 2*x + 3;
end;

procedure TForm1.BerekenClick(Sender: TObject);
begin
ondergrens:=StrtoFloat(ondergr.Text);
bovengrens:=StrtoFloat(bovengr.Text); // ik krijg steeds invalid floating point value bij kommagetal, weet niet hoe ik het moet fixen
stap:=StrToInt(DeelIntervallen.Text);
i:=0;
SetLength(x_rij, stap + 2);
SetLength(Farr, stap + 2);
SetLength(FIarr, stap + 2);
SetLength(FnumIarr, stap + 2);
deelinterval:=(bovengrens-ondergrens)/stap;
Fnum:=0;
FoutMax:=0;

 while (i <= stap) do
    begin
      x_rij[i] := ondergrens + deelinterval * i;
      Farr[i] := F(x_rij[i]);
      FIarr[i] := FI(x_rij[i]) - FI(ondergrens);
      Fonder := Farr[i];
      Fboven := Farr[i-1];
      FnumIarr[i] := deelinterval * 0.5 * (Fboven + Fonder) + FnumIarr[i-1];
      if i = 0 then FnumIarr[i] := 0;
      Resultaat.lines.add(Format('%10.4f %21.8f %21.8f',[x_rij[i], FIarr[i], FnumIarr[i]]));

      Fout := abs(FIarr[i] - FnumIarr[i]);
      if Fout > FoutMax then FoutMax := Fout;
      i := i + 1;

end;
memFout.Text := Format(' %3.8f',[FoutMax]);
end;





procedure TForm1.FormCreate(Sender: TObject);
begin
Resultaat.Clear;
memFout.Clear;
end;

procedure TForm1.WisClick(Sender: TObject);
begin
Resultaat.Clear;
memFout.Clear;
end;

end.