Original

Set operators

The following operators take sets as operands.

Operator	Operation	Operand types	Result type	Example
+	union	set	set	Set1 + Set2
-	difference	set	set	S – T
*	intersection	set	set	S * T
<=	subset	set	Boolean	Q <= MySet
>=	superset	set	Boolean	S1 >= S2
=	equality	set	Boolean	S2 = MySet
<>	inequality	set	Boolean	MySet <> S1
in	membership	ordinal, set	Boolean	A in Set1

The following rules apply to +, -, and *.

· An ordinal O is in X + Y if and only if O is in X or Y (or both). O is in X - Y if and only if O is in X but not in Y. O is in X * Y if and only if O is in both X and Y.

· The result of a +, -, or * operation is of the type set of A..B, where A is the smallest ordinal value in the result set and B is the largest.

The following rules apply to <=, >=, =, <>, and in.

· X <= Y is True just in case every member of X is a member of Y; Z >= W is equivalent to W <= Z. U = V is True just in case U and V contain exactly the same members; otherwise, U <> V is True.

· For an ordinal O and a set S, O in S is True just in case O is a member of S.

Topic groups

See also

About operators

Operator precedence rules

译文

集合运算符

下列运算符接受集合为操作数：

运算符	操作	操作数类型	结果类型	范例
+	并集	集合	集合	Set1 + Set2
-	差集	集合	集合	S – T
*	交集	集合	集合	S * T
<=	子集	集合	Boolean	Q <= MySet
>=	超集	集合	Boolean	S1 >= S2
=	相等	集合	Boolean	S2 = MySet
<>	不等	集合	Boolean	MySet <> S1
in	成员	序数，集合	Boolean	A in Set1

下列规则适用于+、-、* 等运算符：

· 序数O是X + Y的成员，当且仅当O是X的成员或O是Y的成员（或者都是）。O是X - Y的成员当且仅当O是X的成员并且不是Y的成员。O是X * Y的成员当且仅当O是X的成员并且O是Y的成员。

· 运算符+、-或*对集合运算的结果形如set of A..B，这里的A是结果中最小的序数，B是最大的序数。

下列规则适用于<=、>=、=、<>、in等运算符：

· 当X中的每个成员都是Y的成员时，X <= Y的结果为True；Z >= W 等价于W <= Z；当U和V包括完全相同的成员时，U = V的值为True，否则U <> V的值为True。

· 对于序数O和集合S，当O是S的成员时，表达式O in S的值为True。

主题组

相关主题

运算符

运算符优先规则

编者注

序数（Ordinal）和序数型（Ordinal Types）并非仅指如Byte、Word、Integer等整数和整数类型，也包括Char、Boolean等类型。因此“序数”也并非仅指“数”。下面的代码举例说明了序数和集合的类型定义、变量声明和一般使用：

type

TMyBoolean = Boolean;

TMyBooleanSet = set of TMyBoolean;

TWeekDay = (Mon, Tue, Wed, Thu, Fri, Sat, Sun);

TOffDays = set of TWeekDay;

TWorkDays = set of TWeekDay;

var

BSet: TMyBooleanSet;

ODays: TOffDays;

WDays: TWorkDays;

...

BSet := [True];

ODays := [Sat, Sun];

WDays := [Mon, Tue] + [Wed, Thu, Fri] + ODays - [Sun];

...