unit1.~pas

本光盘是《Delphi 7应用教程》一书的配套光盘

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
Type
  aa=2..100;        //定义子界类型
  ssj=set of aa;    //定义集合类型，其基类型为子界类型
var
  ss:ssj;
  m,n,k:Integer;
  t:Real;
  str1,str2:String;
begin
  str1:='';
  str2:='';
  t:=Sqrt(100);       //求最大的除数
  k:=Trunc(t);
  ss:=[2..100];       //对集合变量赋值
  for m:=2 to k do
    for n:=m+1 to 100 do
      if (n mod m=0) then
        ss:=ss-[n]; //能被整除的数被挖掉
  Canvas.TextOut(50,20,'1---100之间的全部素数如下');
  for m:=2 to 100 do
    if (m IN ss) then
      if (m<=41) then
        begin
          str1:=str1+' '+IntToStr(m);
          Canvas.TextOut(10,50,str1);//第一行显示的素数小于等于41
        end
      else
        begin
          str2:=str2+' '+IntToStr(m);
          Canvas.TextOut(10,75,str2);//第二行显示的素数大于41
        end;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  Canvas.FillRect(Form1.ClientRect); //清除窗体上显示的内容
end;

end.