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CS222

Week 14 - Friday. CS222. Last time. What did we talk about last time? OOP in C++ Encapsulation Dynamic dispatch Polymorphism Inheritance Self-reference. Questions?. Project 6. Quotes.

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CS222

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  1. Week 14 - Friday CS222

  2. Last time • What did we talk about last time? • OOP in C++ • Encapsulation • Dynamic dispatch • Polymorphism • Inheritance • Self-reference

  3. Questions?

  4. Project 6

  5. Quotes C makes it easy to shoot yourself in the foot. C++ makes it harder, but when you do, it blows away your whole leg. BjarneStroustrup Developer of C++

  6. C++ Madness

  7. Overloading operators • In C++, you can overload operators, meaning that you can define what + means when used with classes you design • Thus, the following could be legal: Hippopotamus hippo; Sandwich club; Vampiredracula = club + hippo;

  8. Overloading operators • But, what does it mean to "add" a Hippopotamus to a Sandwich and get a Vampire? • Overloading operators is a bad idea • You can get confusing code • Most languages don't allow it • It C++ it is useful in two cases: • To make your objects easy to input/output using iostream • To perform mathematical operations with numerical classes (like Complex!)

  9. (Partial) overloading operators header Complex& operator=( const Complex& complex ); Complex operator+( const Complex& complex ) const; Complex operator-( const Complex& complex ) const; Complex operator-() const; Complex operator*( const Complex& complex ) const;

  10. (Partial) overloading operators implementation Complex& Complex::operator= ( const Complex& complex ) { real = complex.real; imaginary = complex.imaginary; return *this; }

  11. What's all that const? • const, of course, means constant in C++ • In class methods, you'll see several different usages • Const methods make a guarantee that they will not change the members of the object they are called on • intcountCabbages() const; • Methods can take const arguments • void insert(const Coin money); • Methods cant take const reference arguments • void photograph(const Castle& fortress); • Why take a const reference when references are used to change arguments?

  12. Templates

  13. Templates • Allow classes and functions to be written with a generic type or value parameter, then instantiated later • Each necessary instantiation is generated at compile time • Appears to function like generics in Java, but works very differently under the covers • Most of the time you will use templates, not create them

  14. Template method example template<class T> void exchange(T& a, T& b ) { T temp = a; a = b; b = temp; }

  15. Template classes • You can make a class using templates • The most common use for these is for container classes • e.g. you want a list class that can be a list of anything • The STL filled with such templates • Unfortunately, template classes must be implemented entirely in the header file • C++ allows template classes to be separate from their headers, but no major compiler fully supports it

  16. Template class example template<class T> class Pair { private: T x; T y; public: Pair( const T& a, const T& b ) { x = a; y = b; } T getX() const { return x; } T getY() const { return y; } void swap() { T temp = x; x = y; y = temp; } };

  17. STL Standard Template Library

  18. Containers • list • map • multimap • set • multiset • stack • queue • deque • priority_queue • vector

  19. Iterators • Generalization of pointers • No iterators for: • stack • queue • priority_queue • Regular iterator operations: • Postfix and prefix increment and decrement • Assignment • == and != • Dereference • deque and vectoriterators also have <, <=, >, >=, +, -, +=, -+, and []

  20. STL example #include <iostream> #include <vector> #include <string> using namespace std; intmain() { intcount, i; vector<string> words; vector<string>::iterator index; string word; cout << "How many words will you enter? "; cin >> count; for( i = 0; i < count; i++ ) { cin >> word; words.push_back( word ); } for( index = words.begin(); index != words.end(); index++ ) cout << *index << endl; return 0; }

  21. Algorithms • Shuffle • Find • Sort • Count • Always use the ones provided by the container, if available • Functors provided in <functional>

  22. Lab 14

  23. Upcoming

  24. Next time… • Review up to Exam 1 • IDEA evaluations

  25. Reminders • Keep working on Project 6

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