unit1.pas

Numeric Programs

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;
Function FUNC(X:real):real;
Function DERIV(X:real):real;
type
  TForm1 = class(TForm)
    Button1: TButton;
    Memo1: TMemo;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation
//PROGRAM D9R4
//Driver for routine DRENT
uses
  unit2;
  {$R *.DFM}
Function FUNC(X:real):real;
begin
    FUNC:= BESSJ0(X);
end;

Function DERIV(X:real):real;
begin
    DERIV:= -BESSJ1(X);
end;
procedure TForm1.Button1Click(Sender: TObject);
const
  s1='%12.6f'; s2 = '#0';  TOL = 0.000001;  EQL = 0.0001;
var
  F:TextFile;
  AMIN:array[0..20] of real;
  I,J,NMIN,IFLAG:integer;  AX,BX,CX,FA,FB,FC,DBR,XMIN:real;
begin
  //输出计算结果到文件
  AssignFile(F, 'd:\delphi_shu\p9\d9r4.dat');
  Rewrite(F);
  Writeln(F, 'Minima of the function BESSJ0');
  NMIN:= 0;
  Writeln(F, '  Min. #      X       BESSJ0(X)   BESSJ1(X)    DBRENT');
  For I:=1 To 100 do
  begin
    AX:= I;
    BX:=I + 1;
    MNBRAK(AX, BX, CX, FA, FB, FC);
    DBR:= DBRENT(AX, BX, CX, TOL, XMIN);
    If NMIN = 0 Then
    begin
      AMIN[1]:= XMIN;
      NMIN:= 1;
      Writeln(F,'    ',FormatFloat(s2,NMIN),Format(S1,[XMIN]),
        Format(S1,[BESSJ0(XMIN)]),Format(S1,[BESSJ1(XMIN)]),Format(S1,[DBR]));
    end
    Else
    begin
      IFLAG:= 0;
      For J:= 1 To NMIN do
        If Abs(XMIN - AMIN[J]) <= EQL * XMIN Then IFLAG:= 1;
      If IFLAG = 0 Then
      begin
        NMIN:= NMIN + 1;
        AMIN[NMIN]:= XMIN;
        Writeln(F,'    ',FormatFloat(s2,NMIN),Format(S1,[XMIN]),
         Format(S1,[BESSJ0(XMIN)]),Format(S1,[BESSJ1(XMIN)]),Format(S1,[DBR]));
      end;
    end;
  end;
  CloseFile(F);
  //屏幕显示计算结果
  memo1.Lines.LoadFromFile('d:\delphi_shu\p9\d9r4.dat');
end;

end.