《Delphi常用数值算法集》的配书源码

				implementation
				//PROGRAM D12R4
				//Driver for routine ODEINT
				uses
				  unit2;
				  {$R *.DFM}
				procedure DERIVS(X:real; Y:array of real;var DYDX:array of real);
				begin
				    DYDX[1]:= -Y[2];
				    DYDX[2]:= Y[1] - (1 / X) * Y[2];
				    DYDX[3]:= Y[2] - (2 / X) * Y[3];
				    DYDX[4]:= Y[3] - (3 / X) * Y[4];
				end;
				procedure TForm1.Button1Click(Sender: TObject);
				const
				  s1='%14.6f';  s2='%10.4f';NVAR = 4;
				var
				  F:TextFile;  YP:matrx2;
				  VSTART:array[0..NVAR] of real;  XP:array[0..200] of real;
				  I,NOK,NBAD:integer;   X1,X2,H1,EPS,HMIN:real;
				begin
				  SetLength(YP,11,201);
				  X1:=1.0;
				  X2:=10.0;
				  VSTART[1]:= BESSJ0(X1);
				  VSTART[2]:= BESSJ1(X1);
				  VSTART[3]:= BESSJ(2, X1);
				  VSTART[4]:= BESSJ(3, X1);
				  EPS:=0.0001;
				  H1:= 0.1;
				  HMIN:= 0;
				  KMAX:= 100;
				  DXSAV:= (X2 - X1) / 20;
				  ODEINT(VSTART, NVAR, X1, X2, EPS, H1, HMIN, NOK, NBAD, XP, YP);
				  //输出计算结果到文件
				  AssignFile(F, 'd:\delphi_shu\p12\d12r4.dat');
				  Rewrite(F);
				  Writeln(F);
				  Writeln(F,'Successful step:             ',FormatFloat('##0',NOK));
				  Writeln(F,'Bad step:                    ',FormatFloat('##0',NBAD));
				  Writeln(F,'Stored intermediate values:  ',FormatFloat('##0',KOUNT));
				  Writeln(F);
				  Writeln(F,'      X         Integral      BESSJ(3,X)');
				  For I:= 1 To KOUNT do
				        Writeln(F,Format(s2,[XP[I]]),Format(s1,[YP[4, I]]),
				                                 Format(s1,[BESSJ(3, XP[I])]));
				  CloseFile(F);
				  //屏幕显示计算结果
				  memo1.Lines.LoadFromFile('d:\delphi_shu\p12\d12r4.dat');
				end;