quiz_18.17.cpp

/**
 * 实际编写代码检验你对上一题的回答是否正确。
 */

#include <iostream>
using std::cout;
using std::endl;

// using declarations for all the members of namespace Exercise
// are located at the location labeled position 1.
namespace Test0
{
namespace Exercise
{
int ivar = 0;
double dvar = 0;
const int limit = 1000;
} // namespace Exercise

int ivar = 0;

// using Exercise::ivar;
// error C2874: using-declaration causes a multiple declaration of 'Test0::Exercise::ivar'
// So we delete it to make the program compile.
using Exercise::dvar;
using Exercise::limit;

void manip()
{
    double dvar = 3.1416;

    cout << "********** Before call Test0::manip **********" << endl;
    cout << "Exercise::ivar " << Exercise::ivar << endl
         << "Exercise::dvar " << Exercise::dvar << endl
         << "Exercise::limit " << Exercise::limit << endl
         << "Test0::ivar " << Test0::ivar << endl
         << "dvar in function manip" << dvar << endl;

    int iobj = limit + 1; // Exercise::limit + 1
    ++ivar;               // ++ Test0::ivar
    ++Test0::ivar;        // ++ Test0::ivar

    cout << "********** After call Test0::manip  **********" << endl;
    cout << "Exercise::ivar " << Exercise::ivar << endl
         << "Exercise::dvar " << Exercise::dvar << endl
         << "Exercise::limit " << Exercise::limit << endl
         << "Test0::ivar " << Test0::ivar << endl
         << "dvar in function manip " << dvar << endl
         << "iboj in function manip " << iobj << endl;
}
} // namespace Test0

// using declarations for all the members of namespace Exercise
// are located at the location labeled position 2.
namespace Test1
{
namespace Exercise
{
int ivar = 0;
double dvar = 0;
const int limit = 1000;
} // namespace Exercise

int ivar = 0;

void manip()
{
    using Exercise::ivar;
    // using Exercise::dvar;
    // This using declaration causes a redefinition of Test1::Exercise::dvar.
    // So we delete it to make the program compile.
    using Exercise::limit;

    double dvar = 3.1416;

    cout << "********** Before call Test1::manip **********" << endl;
    cout << "Exercise::ivar " << Exercise::ivar << endl
         << "Exercise::dvar " << Exercise::dvar << endl
         << "Exercise::limit " << Exercise::limit << endl
         << "Test1::ivar " << Test1::ivar << endl
         << "dvar in function manip" << dvar << endl;

    int iobj = limit + 1; // Exercise::limit + 1
    ++ivar;               // ++ Exercise::ivar
    ++Test1::ivar;        // ++ Test1::ivar

    cout << "********** After call Test1::manip  **********" << endl;
    cout << "Exercise::ivar " << Exercise::ivar << endl
         << "Exercise::dvar " << Exercise::dvar << endl
         << "Exercise::limit " << Exercise::limit << endl
         << "Test1::ivar " << Test1::ivar << endl
         << "dvar in function manip " << dvar << endl
         << "iboj in function manip " << iobj << endl;
}
} // namespace Test1

// using directive for namespace Exercise is located at the
// location labeled position 1.
namespace Test2
{
namespace Exercise
{
int ivar = 0;
double dvar = 0;
const int limit = 1000;
} // namespace Exercise

int ivar = 0;

using namespace Exercise;

void manip()
{
    double dvar = 3.1416;

    cout << "********** Before call Test2::manip **********" << endl;
    cout << "Exercise::ivar " << Exercise::ivar << endl
         << "Exercise::dvar " << Exercise::dvar << endl
         << "Exercise::limit " << Exercise::limit << endl
         << "Test2::ivar " << Test2::ivar << endl
         << "dvar in function manip" << dvar << endl;

    int iobj = limit + 1; // Exercise::limit + 1
    // ++ivar;
    // error C2872: 'ivar' : ambiguous symbol
    // could be int Test2::ivar or int Test2::Exercise::ivar
    ++Test2::ivar; // ++ Test2::ivar

    cout << "********** After call Test2::manip  **********" << endl;
    cout << "Exercise::ivar " << Exercise::ivar << endl
         << "Exercise::dvar " << Exercise::dvar << endl
         << "Exercise::limit " << Exercise::limit << endl
         << "Test2::ivar " << Test2::ivar << endl
         << "dvar in function manip " << dvar << endl
         << "iboj in function manip " << iobj << endl;
}
} // namespace Test2

// using directive for namespace Exercise is located at the
// location labeled position 2.

namespace Test3
{
namespace Exercise
{
int ivar = 0;
double dvar = 0;
const int limit = 1000;
} // namespace Exercise

int ivar = 0;

void manip()
{
    using namespace Exercise;

    double dvar = 3.1416;

    cout << "********** Before call Test3::manip **********" << endl;
    cout << "Exercise::ivar " << Exercise::ivar << endl
         << "Exercise::dvar " << Exercise::dvar << endl
         << "Exercise::limit " << Exercise::limit << endl
         << "Test3::ivar " << Test3::ivar << endl
         << "dvar in function manip" << dvar << endl;

    int iobj = limit + 1; // Exercise::limit + 1
    // ++ivar;
    // error C2872: 'ivar' : ambiguous symbol
    // could be int Test3::ivar or int Test3::Exercise::ivar
    ++Test3::ivar; // ++ Test3::ivar

    cout << "********** After call Test3::manip  **********" << endl;
    cout << "Exercise::ivar " << Exercise::ivar << endl
         << "Exercise::dvar " << Exercise::dvar << endl
         << "Exercise::limit " << Exercise::limit << endl
         << "Test3::ivar " << Test3::ivar << endl
         << "dvar in function manip " << dvar << endl
         << "iboj in function manip " << iobj << endl;
}
} // namespace Test3

int main()
{
    Test0::manip();
    cout << endl;

    Test1::manip();
    cout << endl;

    Test2::manip();
    cout << endl;

    Test3::manip();
    cout << endl;

    return 0;
}