Advanced Programming Spring 2010

1. Advanced ProgrammingSpring 2010 Standard Template Library (STL) By Eng. YasmineBadr Adapted from www.tantalon.com/pete/embracingstl.ppt

2. Agenda • Introduction • Containers • Iterators • Algorithms • Functors

3. STL • Standard C++ library of: • container classes, • algorithms, and • iterators; • Provides many of the basic algorithms and data structures. • A generic library, i.e. its components are heavily parameterizedalmost every component in STL is a template.

4. Advantages • Standardized • Thin & efficient • Little inheritance; no virtual functions • Small; easy to learn • Flexible and extensible • Naturally open source

5. Containers • Containers contain elements; they “own” the objects • Containers provide iterators that point to its elements. • Containers provide a minimal set of operations for manipulating elements

6. Containers (cont.)

7. Vector • Dynamic array, Contiguous block of memory • reserve(), capacity() • Insert invalidates all iterators if capacity changes • Vectors good at: • Accessing individual elements by their position index (constant time). • Iterating over the elements in any order (linear time). • Add & remove elements from its end (const. time).

8. Deque • Double-ended queue • Fast ins/erase at begin and end • Insert invalidates all iterators • Erase in middle invalidates all iterators • Erase at begin/end invalidates iterators to begin/end

9. List • Doubly-linked list • Fast insert/erase; no random access • Special functions: splice(), merge() • Erase invalidates iterators to erased elements; insert never invalidates any iterators

10. Set • List of sorted elements • Fast retrieval based on key (log N) • Fast insert/erase (log N) • Red-black tree (balanced 2-3-4 tree) • Erase invalidates erased elements • Insert never invalidates any iterators

11. Map • Dictionary of sorted elements • List of sorted key and value pairs

12. Container Adaptors • Implemented by using the fundamental containers classes. • Example adapator code stack<int, deque<int> > stackDeq; stackDeq.push(1); inti = stackDeq.top(); stackDeq.pop();

13. Iterators • Generalization of pointers: they are objects that point to other objects • Often used to iterate over a range of objects: • Typical iteration c<T>::iteratori; for (i = c.begin(); i != c.end() ++i) // forward T t = *i; for (i = c.rbegin(); i != c.rend() ++i) // backward T t = *i;

14. Algorithms • Approx. 60 standard algorithms • searching (e.g. find()) • sorting (e.g. sort()) • mutating (e.g. transform()) • Most functions take the form: • fn(c.begin(), c.end(), ...)

15. Algorithms (cont.) • Examples: #include <algorithm> // return num elements equal to 123 inti = count(c.begin(), c.end(), 123); // negate all elements transform(c.begin(), c.end(),d.begin(), negate<int>()); // apply myFn to all elements for_each(c.begin(), c.end(), myFn); // shuffle the deck random_shuffle(deck.begin(), deck.end());

16. Function Objects (Functors) • C++ objects that can be called like a function to implement “callbacks” • Use C++ operator()(...)

17. Functors (cont.) • Functors that do ordering are called “predicates” • Example: structStlStrPred// “public” class { bool operator()(const char* a, const char* b) { return (strcmp(a, b) == -1); } }; vector<char*> v; sort(v.begin(), v.end(), StlStrPred());