定义一个类，类名为CounterType。这个类的对象用于计数，记录一个非负的整数。为该类写一个默认构造函数，它能将计数器置0；再写一个构造函数，它接收一个参数，用于将计数器设为由参数指定的值。编写两个成员函数，分别使计数能够递增1和递减1。确保任何成员函数都不允许计数器为负值。成员函数void reset( );能在任何时候将计数器的值重置为0。编写两个成员函数，一个返回当前计数器的值，另一个将计数器的值输出到一个流，这个用于输出的函数有一个ostream类型的形式参数（被调用时，实际参数可以是cout）。考虑哪些成员函数定义为常成员函数。
定义主函数，测试这个类。(Define a class named CounterType. The object of this class is used for counting, recording a non negative integer. Write a default constructor for this class. It can set the counter to 0, and then write a constructor, which receives a parameter, which is used to set the counter to the value specified by the parameter. Two member functions are written to increase the count by 1 and decrease by 1 respectively. Make sure that any member function does not allow the counter to be negative. The member function void reset (); can reset the value of the counter to 0 at any time. Two member functions are written, one returns the value of the current counter, and the other outputs the counter value to a stream. The output function has a ostream type formal parameter (when called, the actual parameter can be cout). Consider which member functions are defined as regular member functions.

Define the main function and test the class.)