c-resources/CPlusPlus20ForProgrammers-m.../examples/ch05/fig05_06.cpp

80 lines
2.9 KiB
C++

// fig05_06.cpp
// Scoping example.
#include <iostream>
using namespace std;
void useLocal(); // function prototype
void useStaticLocal(); // function prototype
void useGlobal(); // function prototype
int x{1}; // global variable
int main() {
cout << "global x in main is " << x << '\n';
const int x{5}; // local variable to main
cout << "local x in main's outer scope is " << x << '\n';
{ // block starts a new scope
const int x{7}; // hides both x in outer scope and global x
cout << "local x in main's inner scope is " << x << '\n';
}
cout << "local x in main's outer scope is " << x << '\n';
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 prior value
cout << "\nlocal x in main is " << x << '\n';
}
// useLocal reinitializes local variable x during each call
void useLocal() {
int x{25}; // initialized each time useLocal is called
cout << "\nlocal x is " << x << " on entering useLocal\n";
++x;
cout << "local x is " << x << " on exiting useLocal\n";
}
// 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() {
static int x{50}; // initialized first time useStaticLocal is called
cout << "\nlocal static x is " << x
<< " on entering useStaticLocal\n";
++x;
cout << "local static x is " << x <<
" on exiting useStaticLocal\n";
}
// useGlobal modifies global variable x during each call
void useGlobal() {
cout << "\nglobal x is " << x << " on entering useGlobal\n";
x *= 10;
cout << "global x is " << x << " on exiting useGlobal\n";
}
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