A friend function named spacefriend, which is a friend of class space, and which takes the class object as an argument and prints the value of its variable x.

名为spacefriend的友元函数，它是space类的友元，它的参数是类对象，输出类对象的x变量的值。

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A main function calls the public function func with int arguments of class space.

main函数，它调用space类中使用int参数的公共函数func。

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Probe the function func1 of class space.

探查space类的func1函数。

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