用于开发税务票据管理的软件

				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]) 				      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;