125 lines
2.9 KiB
C++
125 lines
2.9 KiB
C++
// uselessm.cpp -- an otherwise useless class with move semantics
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#include <iostream>
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#include <utility>
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using namespace std;
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// interface
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class Useless
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{
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private:
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int n; // number of elements
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char * pc; // pointer to data
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static int ct; // number of objects
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void ShowObject() const;
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public:
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Useless();
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explicit Useless(int k);
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Useless(int k, char ch);
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Useless(const Useless & f); // regular copy constructor
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Useless(Useless && f); // move constructor
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~Useless();
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Useless operator+(const Useless & f)const;
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// need operator=() in copy and move versions
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void ShowData() const;
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};
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// implementation
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int Useless::ct = 0;
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Useless::Useless()
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{
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++ct;
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n = 0;
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pc = nullptr;
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cout << "default constructor called; number of objects: " << ct << endl;
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ShowObject();
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}
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Useless::Useless(int k) : n(k)
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{
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++ct;
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cout << "int constructor called; number of objects: " << ct << endl;
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pc = new char[n];
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ShowObject();
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}
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Useless::Useless(int k, char ch) : n(k)
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{
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++ct;
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cout << "int, char constructor called; number of objects: " << ct << endl;
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pc = new char[n];
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for (int i = 0; i < n; i++)
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pc[i] = ch;
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ShowObject();
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}
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Useless::Useless(const Useless & f): n(f.n)
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{
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++ct;
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cout << "copy const called; number of objects: " << ct << endl;
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pc = new char[n];
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for (int i = 0; i < n; i++)
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pc[i] = f.pc[i];
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ShowObject();
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}
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Useless::Useless(Useless && f): n(f.n)
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{
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++ct;
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cout << "move constructor called; number of objects: " << ct << endl;
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pc = f.pc; // steal address
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f.pc = nullptr; // give old object nothing in return
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f.n = 0;
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ShowObject();
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}
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Useless::~Useless()
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{
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cout << "destructor called; objects left: " << --ct << endl;
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cout << "deleted object:\n";
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ShowObject();
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delete [] pc;
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}
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Useless Useless::operator+(const Useless & f)const
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{
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cout << "Entering operator+()\n";
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Useless temp = Useless(n + f.n);
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for (int i = 0; i < n; i++)
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temp.pc[i] = pc[i];
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for (int i = n; i < temp.n; i++)
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temp.pc[i] = f.pc[i - n];
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cout << "temp object:\n";
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cout << "Leaving operator+()\n";
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return temp;
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}
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void Useless::ShowObject() const
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{
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cout << "Number of elements: " << n;
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cout << " Data address: " << (void *) pc << endl;
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}
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void Useless::ShowData() const
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{
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for (int i = 0; i < n; i++)
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cout << pc[i];
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cout << endl;
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}
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// application
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int main()
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{
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{
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Useless one(10, 'x');
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Useless two = one; // calls copy constructor
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cout << "object one: ";
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one.ShowData();
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cout << "object two: ";
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two.ShowData();
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Useless three = move(one);
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cout << "object three: ";
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three.ShowData();
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}
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cin.get();
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} |