The Standard Template Library

1. The Standard Template Library Chapter 16

2. Announcement • No class on Friday, Feb. 18 • Engineering Expo • Participate!

3. Objectives • You will be able to use the Standard Template Library list class in C++ programs.

4. C++ Templates • We often need essentially identical classes for use with different kinds of objects. • Examples: • Lists • Stacks • Queues • Compare to arrays

5. C++ Templates • The C++ template permits us to define classes with blanks to be filled in with specific class names at compile time. • Called the template parameter. • A template can have multiple parameters. • The template class cannot be instantiated directly. • It is a pattern from which classes can be created.

6. C++ Templates • Specifying the parameter configures the template as a real class definition. • Filling in the blanks. • When we declare an object of a template class and supply its parameters, the compiler creates a real class. • A template with parameters can be used like a normal class. • Compare to #define.

7. C++ Templates • You can define templates in a C++ program just as you can define normal classes. • Not the subject of this presentation. • We will only be using an existing template. • There is a large library of predefined templates available with any C++ compiler. • The C++ Standard Template Library

8. The Standard Template Library • Big Subject • Brief introduction today. • We will use one template as an example: • The list template

9. STL Components • Containers: • Generic "off-the-shelf" class templates for storing collections of data • Algorithms: • Generic "off-the-shelf" function templates for operating on containers • Iterators: • Generalized pointers that allow algorithms to operate on almost any container

10. The Ten STL Containers Sequential:deque, list, vector Associative:map, multimap, multiset, set Adapters:priority_queue, queue, stack All STL containers use copy semantics.

11. The List Template • The STL list template is a generic linked list class. • We can use it to create a list of objects of any type: • ints • doubles • Circles • Dogs • Cats

12. Frequently Used Methods • size() Returns number of elements • empty() True if list is empty • front() Returns first item • back() Returns last item • push_back() Add item to end of list • pop_back() Remove item from end of list • push_front() Add item to beginning of list • pop_front() Remove item from beginning of list • sort() Sort using < operator • Many more!

13. Example • Create a new project, List_Demo • Add main.cpp #include <iostream> using namespace std; int main(void) { cout << "This is List_Demo\n"; cout << "Normal termination\n"; cin.get(); cin.get(); return 0; }

14. Program Running

15. Using the list template #include <list> ... list<int> int_list;

16. Using the list Template Add to main(): #include <list> ... list<int> int_list; for (int i = 1; i <6 ; ++i) { cout << "Adding " << i << " to end of list\n"; int_list.push_back(i); } cout << "Here is the list:\n"; while (!int_list.empty()) { int next_item = int_list.front(); cout << next_item << endl; int_list.pop_front(); }

17. Program Running

18. Random Numbers #include <iostream> #include <list> #include <cstdlib> using namespace std; int main(void) { list<int> int_list; cout << "This is List_Demo\n"; for (int i = 1; i <6 ; ++i) { int val = rand() % 100; cout << "Adding " << val << " to end of list\n"; int_list.push_back(val); }

19. Program Running

20. Sorting the List int main(void) { list<int> int_list; cout << "This is List_Demo\n"; for (int i = 1; i <6 ; ++i) { int val = rand() % 100; cout << "Adding " << val << " to end of list\n"; int_list.push_back(val); } cout << "Sorting the list\n"; int_list.sort(); cout << "Here is the list:\n";

21. Program Running

22. Sorting into Descending Order bool greater_than(int lhs, int rhs) { return lhs > rhs; } int main(void) { ... cout << "Sorting the list into descending order\n"; int_list.sort(greater_than);

23. Program Running

24. Iterators • The STL defines iterators as generalized pointers that permit user to iterate over all elements in a container. • Permits the same code to be used with various kinds of containers. • Use like a pointer.

25. Using a Iterator cout << "Iterating over the list\n"; list<int>::iterator i; i = int_list.begin(); while (i != int_list.end()) { int next_item = *i; cout << next_item << endl; ++i; }

26. Program Running End of Presentation