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Relational operators

Relational operators are used to compare two operands. The operators =, <>, <=, and >= also apply to sets (see Set operators); = and <> also apply to pointers (see Pointer operators).

Operator	Operation	Operand types	Result type	Example
=	equality	simple, class, class reference, interface, string, packed string	Boolean	I = Max
<>	inequality	simple, class, class reference, interface, string, packed string	Boolean	X <> Y
<	less-than	simple, string, packed string, PChar	Boolean	X < Y
>	greater-than	simple, string, packed string, PChar	Boolean	Len > 0
<=	less-than-or-equal-to	simple, string, packed string, PChar	Boolean	Cnt <= 1
>=	greater-than-or-equal-to	simple, string, packed string, PChar	Boolean	I >= 1

For most simple types, comparison is straightforward. For example, I = J is True just in case I and J have the same value, and I <> J is True otherwise. The following rules apply to relational operators.

· Operands must be of compatible types, except that a real and an integer can be compared.

· Strings are compared according to the ordering of the extended ASCII character set. Character types are treated as strings of length 1.

· Two packed strings must have the same number of components to be compared. When a packed string with n components is compared to a string, the packed string is treated as a string of length n.

· The operators <, >, <=, and >= apply to PChar operands only if the two pointers point within the same character array.

· The operators = and <> can take operands of class and class-reference types. With operands of a class type, = and <> are evaluated according the rules that apply to pointers: C = D is True just in case C and D point to the same instance object, and C <> D is True otherwise. With operands of a class-reference type, C = D is True just in case C and D denote the same class, and C <> D is True otherwise. For more information about classes, see Classes and objects.

Topic groups

See also

About operators

Operator precedence rules

译文

关系运算符

关于运算符运用比较两个操作数。关系运算符 =、<>、<=、>= 也适用于集合（见集合运算符）；= 和 <> 也适用于指针（见指针运算符）。

运算符	操作	操作数类型	结果类型	范例
=	相等	简单类型、类、类引用、接口、串、压缩串	Boolean	I = Max
<>	不等	简单类型、类、类引用、接口、串、压缩串	Boolean	X <> Y
<	小于	简单类型、串、压缩串、PChar	Boolean	X < Y
>	大于	简单类型、串、压缩串、PChar	Boolean	Len > 0
<=	小于或等于	简单类型、串、压缩串、PChar	Boolean	Cnt <= 1
>=	大于或等于	简单类型、串、压缩串、PChar	Boolean	I >= 1

对于大多数简单类型，比较是直接进行的。例如，当I和J具有相同的值是，I = J为True，否则I <> J为True。下列规则适用于关系运算符：

· 除实数和整数可以比较之外，用于比较的操作数必需类型兼容。

· 串的比较依照扩展ASCII字符集的顺序；字符类型被视为长度为1的串。

· 用于比较的两个压缩串，它们的分量（构成压缩串的最小单位）必需在数量上相同。当含有n个分量的压缩串与串作比较时，压缩串被视为长度为n的串。

· 运算符 <、>、<=、>= 适用于PChar类型的操作数，仅当两个指针指向相同的字符数组时。

· 运算符 = 和 <> 可以将类类型和类引用类型作为操作数。对于类类型的操作数，运算符 = 和 <> 的判定依照适用于指针的规则：当C和D指向相同的实例对象时，C = D为True，否则C <> D为True；对于类引用类型的操作数，仅当C和D表示相同的类时，C = D为True，否则C <> D为True。 更多关于类的信息，见类和对象。

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运算符

运算符优先规则