重载二元运算符时，也会隐式重载相应的赋值运算符(如果有)。

When a binary operator is overloaded, the corresponding assignment operator, if any, is also implicitly overloaded.

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一元减号(-)和一元加号(+)与二元加号和减号都是相同的运算符。

The unary minus (-) and unary plus (+) are the same operators as binary minus and plus.

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委托类型也提供二元+运算符，该运算符执行委托串联。

Delegate types also provide a binary + operator, which performs delegate concatenation.

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