d3r1.txt

Numeric Programs

implementation
//PROGRAM D3R1
//Driver for routine TRAPZD
uses
  unit2;
  {$R *.DFM}
Function FUNC(X:real):real;
begin
    FUNC:= Sqr(X) * (Sqr(x) - 2) * Sin(X);
end;

Function FINT(X:real):real;
//Integral of FUNC
var
    AAA:real;
begin
    AAA:= 4 * X * (Sqr(x) - 7) * Sin(X);
    FINT:= AAA - (Sqr(Sqr(x)) - 14 * Sqr(x) + 28) * Cos(X);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  F:TextFile;   I:Integer;
  A,B,S:real;
const
  s1='%16.6f'; s2='###';s3='%9.6f';
  NMAX = 14; PIO2=1.5707963;
begin
  A:=0;
  B:=PIO2;
  //输出计算结果到文件
  AssignFile(F, 'd:\delphi_shu\p3\d3r1.dat');
  Rewrite(F);
  Writeln(F, 'Integral of FUNC with 2^(n-1) points');
  Writeln(F, 'Actual value of integral is: ',
            format(s3,[(fint(b)-fint(a))]));
  Writeln(F, '    n     Approx. Integral');
  For I:= 1 To NMAX do
  begin
      TRAPZD(A,B,S,I);
      Writeln(F,'    ',FormatFloat(s2,I),Format(s1,[s]));
  end;
  CloseFile(F);
  //屏幕显示计算结果
  memo1.Lines.LoadFromFile('d:\delphi_shu\p3\d3r1.dat');
end;