Exer13_48.cpp

#include <iostream>
#include <vector>
#include "Exer13_44_47_49_String.h"
using std::cout;
using std::endl;
using std::vector;
void foo(String x){}
void bar(const String& x){}
String baz()
{
    String ret("world");
    return ret;
}
int main()
{
    cout << "general test1:" << endl;
    String s0;
    String s1("hello");
    String s2(s0);
    String s3 = s1;
    s2 = s1;
    cout << "general test2:" << endl;
    foo(s1);
    bar(s1);
    foo("temporary");
    bar("temporary");
    String s4 = baz();
    cout << "vector test1:" << endl;
    vector<String> svec;
    svec.push_back(s0);
    svec.push_back(s1);
    svec.push_back(baz());
    svec.push_back("good job");
    cout << "vector test2:" << endl;
    vector<String> v;
    for(int i = 0; i != 10; ++i)
        v.push_back("string");
    v.clear();
    if(v.empty())
        cout << "v is empty" << endl;
    return 0;
}
// ******results******
// general test1:
// String(const String&) is called
// String(const String&) is called
// String& operator=(const String&) is called
// general test2:
// String(const String&) is called
// vector test1:
// String(const String&) is called
// String(const String&) is called
// String(const String&) is called
// String(const String&) is called
// String(const String&) is called
// String(const String&) is called
// String(const String&) is called
// vector test2:
// String(const String&) is called
// ...(25 times in total)

// Note #1: part of the tests come from
// https://github.com/Mooophy/Cpp-Primer/blob/master/ch13/ex13_48.cpp
// which is quoted from
// http://coolshell.cn/articles/10478.html

// Note #2: the result shows that copy constructor is called more times than
// push_back is called.