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100 lines
2.0 KiB
C++
100 lines
2.0 KiB
C++
#include <iostream>
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#include <vector>
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class Animal {
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public:
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Animal() {
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std::cout << "constructor" << std::endl;
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}
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Animal(const Animal& other) {
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std::cout << "copy constructor (" << &other << ")" << std::endl;
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}
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// Note: using *virtual* does the difference here!
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virtual void makeSound() const {
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std::cout << "<generic animal sound> from " << this << std::endl;
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}
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Animal& operator= (Animal &a) {
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std::cout << "lol, operator= of " << this;
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std::cout << "(arg: " << &a << ")" << std::endl;
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return *this;
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}
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};
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class Cow : public Animal {
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public:
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void makeSound() const {
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std::cout << "Mooh. from " << this << std::endl;
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}
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};
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class Cat : public Animal {
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public:
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void makeSound() const {
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std::cout << "Meow? from " << this << std::endl;
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}
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};
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void call(Animal a) {
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a.makeSound();
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}
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void callref(Animal &a) {
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a.makeSound();
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}
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void callptr(Animal* a) {
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a->makeSound();
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}
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int main() {
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Cat cat;
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Cow cow;
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std::cout << "== Some animals" << std::endl;
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Animal animal;
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animal.makeSound();
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std::cout << "== animal" << std::endl;
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call(animal);
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callref(animal);
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callptr(&animal);
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std::cout << "== cat" << std::endl;
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animal = cat; // <- lol, operator
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animal.makeSound();
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call(cat);
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callref(cat); // <- meow
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callref(animal); // <- generic
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callptr(&cat); // <- meow
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std::cout << "== cow" << std::endl;
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animal = cow; // <- lol, operator
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animal.makeSound();
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call(cow);
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callref(cow); // <- mooh
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callptr(&cow); // <- mooh
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std::cout << "== refs" << std::endl;
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Animal &aref = cat;
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aref.makeSound(); // <- meow
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aref = cow; // <- lol, operator
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aref.makeSound(); // <- meow, still
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std::cout << "== vector<Animal>:" << std::endl;
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// Does nothing:
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std::vector<Animal> animals = { cat, cow }; // <- Copies
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for (auto &a : animals) {
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a.makeSound();
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}
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std::cout << "== vector<Animal*>:" << std::endl;
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// Meow? Mooh.
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std::vector<Animal*> animalptrs = { &cat, &cow };
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for (auto &a : animalptrs) {
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a->makeSound();
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}
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}
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