fig06_12.cpp

c++大学教程第5版的配套书源代码

// Fig. 6.12: fig06_12.cpp
// A scoping example.
#include <iostream>
using std::cout;
using std::endl;

void useLocal( void ); // function prototype
void useStaticLocal( void ); // function prototype
void useGlobal( void ); // function prototype

int x = 1; // global variable

int main()
{
   int x = 5; // local variable to main

   cout << "local x in main's outer scope is " << x << endl;

   { // start new scope
      int x = 7; // hides x in outer scope

      cout << "local x in main's inner scope is " << x << endl;
   } // end new scope

   cout << "local x in main's outer scope is " << x << endl;

   useLocal(); // useLocal has local x
   useStaticLocal(); // useStaticLocal has static local x
   useGlobal(); // useGlobal uses global x
   useLocal(); // useLocal reinitializes its local x
   useStaticLocal(); // static local x retains its prior value
   useGlobal(); // global x also retains its value

   cout << "\nlocal x in main is " << x << endl;
   return 0; // indicates successful termination
} // end main

// useLocal reinitializes local variable x during each call
void useLocal( void )
{
   int x = 25; // initialized each time useLocal is called

   cout << "\nlocal x is " << x << " on entering useLocal" << endl;
   x++;
   cout << "local x is " << x << " on exiting useLocal" << endl;
} // end function useLocal

// useStaticLocal initializes static local variable x only the
// first time the function is called; value of x is saved
// between calls to this function
void useStaticLocal( void )
{
   static int x = 50; // initialized first time useStaticLocal is called 

   cout << "\nlocal static x is " << x << " on entering useStaticLocal" 
      << endl;
   x++; 
   cout << "local static x is " << x << " on exiting useStaticLocal" 
      << endl;
} // end function useStaticLocal

// useGlobal modifies global variable x during each call
void useGlobal( void )
{
   cout << "\nglobal x is " << x << " on entering useGlobal" << endl;
   x *= 10;
   cout << "global x is " << x << " on exiting useGlobal" << endl;
} // end function useGlobal




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