1 STL Containers Copyright Kip Irvine, All rights reserved. Only students enrolled in a class at Florida International University may copy or print the contents of this slide show. Last update: 3/30/2003

Copyright 2003, Kip R.Irvine2 Standard Template Library (STL) Created by Alexander Stepanov and Meng Lee at Hewlett-Packard Key components: containers, iterators, algorithms Helps you avoid having to re-invent standard container implementation code Design choice: generic classes chosen for runtime efficiency more efficient than object-based containers that use polymorphism

Copyright 2003, Kip R.Irvine3 Standard Template Library (STL) Recently incorporated into the Standard C++ Library STL Programmers' Guide available at: Latest release: 3.3, June 2000.

Copyright 2003, Kip R.Irvine4 Types of Containers Sequence containers vector deque list Associative containers set, multiset map, multimap Container adapters stack queue priority_queue

Copyright 2003, Kip R.Irvine5 Required Headers Class name same as header:,,,, Also: queue, priority_queue set, multiset map, multimap

Copyright 2003, Kip R.Irvine6 Error Handling Exceptions are never thrown by STL classes In fact, exceptions and templates don't mix Very little error checking exists in STL classes

Copyright 2003, Kip R.Irvine7 Common Typedefs value_type type of element stored in the container reference, const_reference reference to type of element stored in the container pointer pointer to the type of element stored in the container iterator, const_iterator a forward iterator that points to the type of element stored in the container reverse_iterator, const_reverse_iterator a reverse iterator that points to the type of element stored in the container

Copyright 2003, Kip R.Irvine8 Common typedefs in STL (cont) difference_type type of the result of subtracting two iterators size_type type used to count items in a container, and index through a sequence container

Copyright 2003, Kip R.Irvine9 Common Member Functions default constructor, copy constructor, destructor empty max_size max number of elements for a container size number of elements currently in the container operator = assign one container to another overloaded, >=, ==, != swap

Copyright 2003, Kip R.Irvine10 Common Member Functions beginreturns an iterator (-> first element) endreturns an iterator (-> after last element) eraseerase 1 or more elements clearerase all elements rbeginreturns reverse_iterator rendreturns reverse_iterator

Copyright 2003, Kip R.Irvine11 Element Types for Containers Must have correct copy semantics bitwise default, or overload the assignment ( = ) operator and copy constructor Provide operator < and operator ==

Copyright 2003, Kip R.Irvine12 Types of Iterators Input Iterator (InIt) Used to read an element from a container Moves only in forward direction, one element at a time Cannot pass through a sequence twice Output Iterator (OutIt) Used to write an element to a container Moves only in forward direction, one element at a time Cannot pass through a sequence twice Each iterator's capabilities are a superset of the previously listed iterators.

Copyright 2003, Kip R.Irvine13 Types of Iterators (cont) Forward Iterator (FwdIt) reads and writes in forward direction only retains its position in the container Bidirectional Iterator (BidIt) reads and writes in both directions retains its position in the container Random-Access Iterator (RadIt) reads and writes in randomly accessed positions permits pointer arithmetic Each iterator's capabilities are a superset of the previously listed iterators.

Copyright 2003, Kip R.Irvine14 Iterator Support, by Container stack, queue, priority_queue:no iterators list, set, multiset, map, multimap:bidirectional vector, deque:random

Copyright 2003, Kip R.Irvine15 Invalidating Iterators Some, but not all operations on containers invalidate iterators result: iterator can be stale remember that iterators are basically pointers Examples: list.push_back( ) does not invalidate iterators vector.push_back( ) invalidates all iterators list.erase( ) invalidates only iterators that pointed to the deleted elements check the documentation for each method!

Copyright 2003, Kip R.Irvine16 Sequence Containers

Copyright 2003, Kip R.Irvine17 vector Container sequence container with contiguous memory locations permits direct access to any member via [ ] or at( ) automatically doubles its allocation when current size is exceeded insertion and deletion only permitted at the tail supports random-access iterators all lesser iterators also

Copyright 2003, Kip R.Irvine18 Common vector Functions push_back, pop_back add to end, remove from end size current number of elements capacity storage allocation size begin, end return iterator and const_iterator rbegin, rend return reverse_iterator and const_reverse_iterator front, back return first and last elements

Copyright 2003, Kip R.Irvine19 Common vector Functions at( ) operator [ ] (also found in deque)

Copyright 2003, Kip R.Irvine20 list Sequence Container efficient insertion and deletion at any location deque is more efficient if insertions and deletions are at the ends of the container implemented as doubly-linked list supports bidirectional iterators does not support at( ) or operator [ ]

Copyright 2003, Kip R.Irvine21 list Operations operations not found in vectors: void splice( iterator iter, list & X ) removes values from list X and inserts them into the current list in the position immediately before position iter void push_front( const T & X ) inserts element X at the front of the list void pop_front( ) removes one element from the front of the list void remove( const T& x ) removes all elements found to be equal to X

Copyright 2003, Kip R.Irvine22 Unique list Operations void unique() Removes from the current list every element that is equal to its preceding element void merge( list & other ) Removes from the list other and insert them in sorted order into the current list void reverse() Reverses the order of elements in the current list void sort() Sorts the list in ascending order by automatically calling the < operator function to compare pairs of elements void sort( greater pred ) Sorts the list in descending order by automatically calling the < operator function to compare pairs of elements

Copyright 2003, Kip R.Irvine23 Creating a list list scores; scores.push_back( 20 ); scores.push_front( 10 ); scores.pop_front( ); scores.remove( 20 );// removes "20" cout << "size: " << scores.size( ) << endl; List of lists containing strings: list > L; Disable Microsoft VS 6.0 warning message that appears when templates contain strings: #ifdef _DEBUG #pragma warning( disable : 4786 ) #endif

Copyright 2003, Kip R.Irvine24 Printing a list template void print( const list & aList ) { if ( aList.empty() ) cout << "List is empty"; else { list ::const_iterator I = aList.begin( ); for( ; I != aList.end( ); I++ ) cout << *I << ", "; cout << endl; }

Copyright 2003, Kip R.Irvine25 Removing list Duplicates list scores; scores.push_back( 10 ); scores.push_back( 20 ); scores.push_back( 30 ); scores.unique( ); print( scores );// 10, 20, 30

Copyright 2003, Kip R.Irvine26 List of Lists typedef list stringList; stringList s; s.push_back( "Dan" ); s.push_back( "Bill" ); s.push_back( "Anne" ); // a list containing lists of strings list L; L.push_back( s );

Copyright 2003, Kip R.Irvine27 Associative Containers

Copyright 2003, Kip R.Irvine28 Associative Containers keys are always kept in sorted order iterator always traverses in sort order set – single key values equivalent to Java's TreeSet multiset – duplicate keys allowed map – contains pairs (key, value) key is unique equivalent to Java's TreeMap multimap key need not be unique

Copyright 2003, Kip R.Irvine29 Sets: Three Ways to Insert Items insert single value, returning an iterator iterator insert( const value_type & x); start searching for insert point after iterator it: iterator insert( iterator it, const value_type & x ); insert sequence of elements in the range [first, last): void insert( const value_type * first, const value_type * last );

Copyright 2003, Kip R.Irvine30 Examples: Inserting and Finding Create a multiset and insert single values: multiset B; B.insert( 30 ); B.insert( 20 ); Insert an array: const int SIZE = 5; int array1[SIZE] = { 10,20,30,30,40 }; B.insert( array1, array1 + SIZE ); Find a value: multiset ::const_iterator I = B.find( 30 );

Copyright 2003, Kip R.Irvine31 Using typedef Use typedef to simplify type definitions: typedef multiset msetInt;. msetInt A; typedef multiset ::const_iterator msetIter;. msetIter = A.insert( 30 );

Copyright 2003, Kip R.Irvine32 Printing a Multiset template void print( const multiset & aSet ) { if ( aSet.empty() ) cout << "Set is empty"; else { multiset ::const_iterator I = aSet.begin( ); for( ; I != aSet.end( ); I++ ) cout << *I << ", "; }

Copyright 2003, Kip R.Irvine33 set Associative Container keys are unique attempt to insert duplicate key is ignored same functions as multiset

Copyright 2003, Kip R.Irvine34 map Associative Container unique keys and their associated values each key is mapped to a single value values do not have to be unique fast storage and retrieval sorted in order according to keys Iterators point to pair fields named first, second values can be inserted using [ ] operator see: mapdemo.cpp

Copyright 2003, Kip R.Irvine35 Function Objects template class that contains a function the function can be used in the same way as operator ( ) make STL more flexible permit sorting on your own criteria predefined objects in STL: divides equal_to greater greater_equal less etc.

Copyright 2003, Kip R.Irvine36 Function Object Example Default comparison of STL container objects when sorting uses the < operator: template class less { public: bool operator()(const T & x, const T & y) const { return x < y; } };

Copyright 2003, Kip R.Irvine37 Function Object Example When you declare a set, you have the option of specifying a function object that will determine the positions where new elements are inserted. Example: set of strings named myStringSet: set > myStringSet;

Copyright 2003, Kip R.Irvine38 Binary Function Example Base class binary_function defines overloaded ( ) operator with two arguments. This function object squares a value and adds it to a total: template class SumSquaresClass :public binary_function { public: const T operator( )( const T & total, const T & value ) { return total + value * value; } };

Copyright 2003, Kip R.Irvine39 Binary Function Example (cont) accumulate( first, last, startVal, pred ) The STL defines an accumulate function that accumulates a sum over a collection. the optional pred parameter can be a function or a function object vector v;... int sum = accumulate( v.begin( ), v.end( ), 0, SumSquaresClass () );

Copyright 2003, Kip R.Irvine40 Optional Information

Copyright 2003, Kip R.Irvine41 deque sequence container pronounced "deck" provides benefits of vector and list in the same container rapid indexed access (like vector) efficient insertion & deletion at its ends (like list) supports random-access iterators often used for FIFO queue noncontiguous memory layout

Copyright 2003, Kip R.Irvine42 Common deque operations push_back( ) push_front( ) pop_back( ) pop_front( ) size( ) operator [ ] at( )

Copyright 2003, Kip R.Irvine43 deque Example #1 Create a deque containing pointers to strings: deque mque; mque.push_back( new Message( "John", "How are you?" )); mque.push_back( new Message( "Sam", "What's happening?" )); mque.push_back( new Message( "Anne", "What's for dinner?" )); mque.push_back( new Message( "Bill", "Let's go surfing!" ));

Copyright 2003, Kip R.Irvine44 deque Example #1 Serve all messages from the front of the queue until the queue is empty: while( mque.size( ) > 0 ) { cout << **(mque.begin( )) << endl; mque.pop_front( ); } see dequeDemo.cpp

Copyright 2003, Kip R.Irvine45 The End