fig03_12.cpp

《c＋＋大学教程》源码

// Fig. 3.12: fig03_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;

      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 << endl << "local 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 )
{
   // initialized first time useStaticLocal is called.
   static int x = 50;  

   cout << endl << "local 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 << endl << "global x is " << x 
        << " on entering useGlobal" << endl;
   x *= 10;
   cout << "global x is " << x 
        << " on exiting useGlobal" << endl;
   
} // end function useGlobal

/**************************************************************************
 * (C) Copyright 1992-2003 by Deitel & Associates, Inc. and Prentice      *
 * Hall. All Rights Reserved.                                             *
 *                                                                        *
 * DISCLAIMER: The authors and publisher of this book have used their     *
 * best efforts in preparing the book. These efforts include the          *
 * development, research, and testing of the theories and programs        *
 * to determine their effectiveness. The authors and publisher make       *
 * no warranty of any kind, expressed or implied, with regard to these    *
 * programs or to the documentation contained in these books. The authors *
 * and publisher shall not be liable in any event for incidental or       *
 * consequential damages in connection with, or arising out of, the       *
 * furnishing, performance, or use of these programs.                     *
 *************************************************************************/