13.1.4节目练习

1. 练习13.14

#include <iostream>
using namespace std;class numbered
{
private:    static int seq;
public:numbered() { mysn = seq++; }int mysn;
};int numbered::seq = 0;void f(numbered s) 
{ cout << s.mysn << endl; 
}int main()
{numbered a, b = a, c = b;f(a);f(b);f(c);
}

2. 练习13.15

#include <iostream>
using namespace std;class numbered
{
private:static int seq;
public:numbered() { mysn = seq++; }numbered(const numbered &n ) { mysn = seq++; }int mysn;
};int numbered::seq = 0;void f(numbered s)
{cout << s.mysn << endl;
}int main()
{numbered a, b = a, c = b;f(a);f(b);f(c);
}

1. 练习13.15

#include <iostream>
using namespace std;class numbered
{
private:static int seq;
public:numbered() { mysn = seq++; }numbered(const numbered &n ) { mysn = seq++; }int mysn;
};int numbered::seq = 0;void f(numbered &s)
{cout << s.mysn << endl;
}int main()
{numbered a, b = a, c = b;f(a);f(b);f(c);
}

13.2节练习

#include <string>class HasPtr {
public:HasPtr(const std::string &s = std::string()) : ps(new std::string(s)), i(0) {}HasPtr(const HasPtr &hp) : ps(new std::string(*hp.ps)), i(hp.i) {}HasPtr& operator=(const HasPtr &hp) {auto new_p = new std::string(*hp.ps);delete ps;ps = new_p;i = hp.i;return *this;}~HasPtr() { delete ps;} 
private:std::string *ps;int i;
};

13.2.2练习

• 练习13.27

#include <string>class HasPtr {
public:HasPtr(const std::string& s = std::string()) : ps(new std::string(s)), i(0), use(new size_t(1)) {}HasPtr(const HasPtr& hp) : ps(hp.ps), i(hp.i), use(hp.use) { ++* use; }HasPtr& operator=(const HasPtr& rhs);
private:std::string* ps;int i;size_t* use;
};HasPtr& HasPtr::operator=(const HasPtr& rhs)
{++* rhs.use;if (-- * use == 0){delete ps;delete use;}ps = rhs.ps;i = rhs.i;use = rhs.use;return *this;
}