d3r9.txt

来自「《Delphi常用数值算法集》的配书源码」· 文本 代码 · 共 45 行

implementation
//PROGRAM D3R9
//Driver for routine GAULEG
uses
  unit2;
  {$R *.DFM}

Function FUNC(X:real):real;
begin
    FUNC:= X * Exp(-X);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  F:TextFile;   I,NPOINT:Integer;
  X1,X2,X3,XX:real;
  X,W:array[0..10] of real;
const
  s1='%14.6f'; s2='%10.6f'; s3='###';
begin
  NPOINT:=10;
  X1:=0;
  X2:=1;
  X3:=10;
  GAULEG(X1,X2,X,W,NPOINT);
  //输出计算结果到文件
  AssignFile(F, 'd:\delphi_shu\p3\d3r9.dat');
  Rewrite(F);
  Writeln(F, '  #         X(I)          W(I)');
  For I:= 1 To NPOINT do
    Writeln(F,'  ',FormatFloat(s3,I),Format(s1,[X[I]]),
           Format(s1,[W[I]]));
  //Demonstrate the use of GAULEG for an integral
  GAULEG(X1,X3,X,W,NPOINT);
  XX:=0;
  For I:= 1 To NPOINT do
    XX:= XX + W[I] * FUNC(X[I]);
  Writeln(F);
  Writeln(F,'Integral from GAULEG: ',Format(s2,[XX]));
  Writeln(F,'Actual value: ',Format(s2,[1-(1+x3)*exp(-x3)]));

  CloseFile(F);
  //屏幕显示计算结果
  memo1.Lines.LoadFromFile('d:\delphi_shu\p3\d3r9.dat');
end;