d2r3.txt

《Delphi常用数值算法集》的配书源码

implementation
//PROGRAM D2R3
//Driver for routine SPLINE
uses
  unit2;
  {$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
var
  X,Y,Y2:array[0..20] of real;
  YP1,YPN:real;
  F:TextFile;  I:Integer;
const
  N=20; PI=3.1415926; s1='%12.6f';  s3='%6.2f';
begin
  For I:=1 to N do
  begin
      X[I]:= I * PI / N;
      Y[I]:= SIN(X[I]);
  end;
  //用三次样条函数计算二阶导数
  YP1:= COS(X[1]);
  YPN:= COS(X[N]);
  SPLINE(X,Y,N,YP1,YPN,Y2);
  //输出计算结果到文件
  AssignFile(F, 'd:\delphi_shu\p2\d2r3.dat');
  Rewrite(F);
  Writeln(F, 'Second-derivative for sin(x) from 0 to PI');
  Writeln(F,'             spline         actual');
  Writeln(F, '  angle     2nd deriv.     2nd deriv.');
  for I:=1 To N do
    Writeln(F,Format(s3,[X[I]]),'  ',Format(s1,[Y2[I]]),'    ',
          Format(s1,[-SIN(X[I])]));

  CloseFile(F);
  //屏幕显示计算结果
  memo1.ScrollBars:=ssVertical;
  memo1.Lines.LoadFromFile('d:\delphi_shu\p2\d2r3.dat');
end;