传回布林值，指出运算式是否可以评估为数字。

Returns a Boolean value indicating whether an expression can be evaluated as a number.

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将指定的布林值转换为相等的单精确度浮点数。

Converts the value of the specified object to a single-precision floating-point number.

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传回的布林值将说明物件是否为某个特定类别的执行个体。

Returns a Boolean value that indicates whether or not an object is an instance of a particular class.

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