Spring 2010 Advanced Programming

Section 1-STL

Computer Engineering DepartmentFaculty of EngineeringCairo University

Advanced ProgrammingSpring 2010

Standard Template Library (STL)

By Eng. Yasmine Badr

Adapted from

www.tantalon.com/pete/embracingstl.ppt

Spring 2010 Advanced Programming

Section 1-STL

Agenda

• Introduction• Containers• Iterators• Algorithms• Functors

Spring 2010 Advanced Programming

Section 1-STL

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 parameterizedalmost every component in STL is a template.

Spring 2010 Advanced Programming

Section 1-STL

Advantages

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

Spring 2010 Advanced Programming

Section 1-STL

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

Spring 2010 Advanced Programming

Section 1-STL

Containers (cont.)

Container Description Keysvector dynamic array

deque dynamic array -- both ends

list linked list

set sorted list of keys no duplicate keys

map sorted list of key and value pairs no duplicate keys

multiset sorted list of keys duplicate keys OK

multimap sorted list of key and value pairs duplicate keys OK

valarray similar to vector<T>, where T is numeric, but optimized for numeric ops

bitset similar to vector<bool>, but fixed size and includes bit operators

Spring 2010 Advanced Programming

Section 1-STL

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).

Spring 2010 Advanced Programming

Section 1-STL

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

Spring 2010 Advanced Programming

Section 1-STL

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

Spring 2010 Advanced Programming

Section 1-STL

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

Spring 2010 Advanced Programming

Section 1-STL

Map

• Dictionary of sorted elements• List of sorted key and value pairs

Spring 2010 Advanced Programming

Section 1-STL

Container Adaptors

• Implemented by using the fundamental containers classes.

• Example adapator code

stack<int, deque<int> > stackDeq;stackDeq.push(1);int i = stackDeq.top();stackDeq.pop();

Adaptor Example containers Default container

stack list, deque, vector deque

queue list, deque deque

priority_queue list, deque, vector vector

Spring 2010 Advanced Programming

Section 1-STL

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>::iterator i;for (i = c.begin(); i != c.end() ++i) // forward T t = *i;

for (i = c.rbegin(); i != c.rend() ++i) // backward T t = *i;

Spring 2010 Advanced Programming

Section 1-STL

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(), ...)

Spring 2010 Advanced Programming

Section 1-STL

Algorithms (cont.)

• Examples:

#include <algorithm>

// return num elements equal to 123int i = count(c.begin(), c.end(), 123);

// negate all elementstransform(c.begin(), c.end(),d.begin(), negate<int>());

// apply myFn to all elementsfor_each(c.begin(), c.end(), myFn);

// shuffle the deckrandom_shuffle(deck.begin(), deck.end());

Spring 2010 Advanced Programming

Section 1-STL

Function Objects (Functors)

• C++ objects that can be called like a function to implement “callbacks”

• Use C++ operator()(...)

Spring 2010 Advanced Programming

Section 1-STL

Functors (cont.)

• Functors that do ordering are called “predicates”

• Example:

struct StlStrPred // “public” class{ bool operator()(const char* a, const char* b) { return (strcmp(a, b) == -1); } };

vector<char*> v;sort(v.begin(), v.end(), StlStrPred());