集合

集合类型表示一组值，该组值由集合所依据的有序类型定义。定义集合的常用有序类型不多，一般为枚举类型或子界类型。如果子界类型取值为 1..3，那么基于它的集合类型值可以是 1、或 2、或 3、或 1 和 2、或 1 和 3、或 2 和 3、或取所有 3 个数、或一个数也没有。

//定义
type
  Uppercase = 'A'..'Z';
  Letters = set of Uppercase;  //基于子界定义

  TBorderIcon = (biSystemMenu, biMinimize, biMaximize, biHelp);
  TBorderIcons = set of TBorderIcon;  //基于枚举定义
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//应用
type
  Uppercase = 'A'..'Z';
  Letters = set of Uppercase;  //基于子界定义
var
  L1, L2, L3: Letters;
begin
  L1 := ['A', 'B', 'C'];
  L2 := ['K'];
  L3 := [];

  if 'A' in L1 then ShowMessage('true');  //true
  if L2=['K'] then ShowMessage('true');  //true
  if L3=[] then ShowMessage('true');  //true
end;
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//判断是否属于集合
type
  TSet = set of (A,B,C);
var
  set1: TSet;
begin
  set1 := [A,B];
  if A in set1 then
    ShowMessage('集合 set1 包含 A');
end;
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//集合元素的增减
type
  TSet = set of (A,B,C);
var
  set1: TSet;
begin
  set1 := [A];

  set1 := set1 + [B];  //增加一个元素
  Include(set1,B);     //增加一个元素

  set1 := set1 - [B];  //排除一个元素
  Exclude(set1,B);     //排除一个元素
end;
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//集合添加元素举例
type
  TCharSet = set of char;
var
  character: 'a'..'z';
  charSet: TCharSet;
  word: string;
begin
  charSet := [];
  for character in [Low(character) .. High(character)] do
  begin
    if character in ['d', 'e', 'l', 'p', 'h', 'i'] then
    begin
      Include(charSet, character);
    end;
  end;

  for character in charSet do
  begin
    word := word + character;
  end;

  ShowMessage(word);  //dehilp
end;

//交集
procedure TForm1.FormCreate(Sender: TObject);
type
  TSet = set of (A,B,C,D,E,F,G);
var
  set1,set2,set3: TSet;
begin
  set1 := [A,B,C];
  set2 := [C,D,E];
  set3 := set1 * set2;

  {现在 set3 应该是 [C], 测试下}
  if set3 = [C] then ShowMessage('Ok');
end;