2.2.4 名字的作用域-嵌套的作用域

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书中页数：P43
代码名称：scope_levels.cc

#include <iostream>

// Program for illustration purposes only: It is bad style for a function
// to use a global variable and also define a local variable with the same name

int reused = 42;  // reused has global scope

int main()
{
	int unique = 0; // unique has block scope

	// output #1: uses global reused; prints 42 0
	std::cout << reused << " " << unique << std::endl;   

	int reused = 0; // new, local object named reused hides global reused

	// output #2: uses local reused; prints 0 0
	std::cout << reused << " " <<  unique << std::endl;  

	// output #3: explicitly requests the global reused; prints 42 0
	std::cout << ::reused << " " <<  unique << std::endl;  

	return 0;
}