1. Introduction to the ISO C++ Standard Template Library (STL)
Jean-Paul Rigault
Professor, École supérieure en sciences informatiques (ESSI)
University of Nice Sophia Antipolis
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2. Purpose of the STL Language run-time support
Implementation characteristics
Implementation limits
Standard function with a machine-dependent optimal implementation
Non primitive, yet portable objects
Extensibility
Foundation for other libraries
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3. Implementation Constraints
Usable directly and easily
Efficient
Neutral policy
Primitive
Complete
Compatible with base types
Type-safe
Support for all programming styles
Extensible
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4. Organization of the C++ STL
Namespace std
Header files
Recover ANSI C header files (<cXXXX>  <XXXX.h>)
Library elements
Containers, iterators, algorithms, general utilities, diagnostics, strings, input-output, localization, basic run-time support, (numerical elements)
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5. Containers Homogeneous contents Homogeneous interface
Common member-functions
Iterators
Specific member-functions
Parametrized memory allocation scheme (template parameter)
default allocator : allocator<T>
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6. Containers : Different Types
Basic Containers
vector<T> vector with automatic (re)allocation
list<T> doubly linked sequence (list)
dequeue<T> sequence with optimized indexing
Container adapters
stack<T> LIFO
queue<T> FIFO
priority_queue<T> queue with priority (operator <)
Associative containers
map<K, T> associative array without duplicate (K is the key)
multimap<K, T> associative array with duplicate (K is the key)
set<K> set (without duplicate) of K
multiset<K> set with duplicate (i.e., bag) of K
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7. Containers : Iterators (1)
Model : sequence and extended pointer
rend()
begin()
iterator p
rbegin()
end() -- ++ *p
list<int> L;
for (int i = 0; i < N; i++) L.push_front(i);
list<int>::const_iterator it;
for (it = L.begin(); it != L.end(); it++)
cout << *it << ' ';
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8. Containers : Iterators (2)
Reverse iteration
Use a reverse iterator
list<int>::const_reverse_iterator rit; for (rit = L.rbegin(); rit != L.rend(); rit++)
cout << *rit << ' ';
Non const iterator
Allow modification of container elements
list<int>::reverse_iterator rit;
for (rit = L.rbegin(); rit != L.rend(); rit++) *rit = 10;
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9. Containers : Iterators (3)
Using iterators as interval bounds
list<int> L; list<int>::iterator it;
int n;
...
for (n = 0, it = L.begin();
(it = find(it, L.end(), 3) != L.end(); it++)
{ n++; }
Iterator intervals always include left bound and exclude right one ([ … [)
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10. Containers: Common Characteristics
Member-types
value_type type of value
iterator ~ value_type*
const_iterator ~ const value_type*
reverse_iterator ~ value_type*
const_reverse_iterator ~ const value_type*
reference ~ value_type&
const_reference ~ const value_type&
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11. Containers : Common Characteristics Common Member-Functions (1)
Iteration
begin() “Point” to first element
end() “Point” to just after last element
rbegin() “Point” to first element in reverse order
rend() “Point” to just after last element in reverse order
Access to contents
front() Reference to first element
last() Reference to last element
[] Indexing without bound checking (N/A for lists)
at() Indexing with bound checking (N/A for lists)
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12. Containers : Common Characteristics Common Member-Functions (2)
Operations on lists, stacks, and queues
push_back() Append (add after last)
pop_back() Remove last element and return its value
push_front() Prepend (add before first)
pop_front() Remove first element and return its value
Operations on list (sequence)
insert() Insert before an element
erase() Remove an element
clear() Remove all elements
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13. Containers : Common Characteristics Common Member-Functions (3)
Miscellaneous operations
size() Number of elements
empty() Is the container empty ?
max_size() Maximum possible size
swap() Swap two elements
== != < Comparisons
Assignments
assign(n) Assign n elements (to their default value)
assign(n, x) Assign n copies of x
assign(first, last) Assign all elements between iterators
first and last to default value
= Ordinary (copy) assignment
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14. Containers : Common Characteristics Common Member-Functions (4)
Construction and destruction
container() Empty container
container(n) Container with n elements
(initialized to their default value)
container(n, x) Container with n copies of
element x
container(first, last) Container with elements copied from interval between iterators
first et last
container(other_container) Copy of container
~container() Destructor
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15. Containers : Remarks (1)
Constraints on the elements (value_type)
Default constructor
Define the "zero" of the type
Copy operations
For ordered containers, “less than” operator (<)
If no equality operator, “less than” is used : a == b  !(a < b) && !(b < a)
Vectors
No arithmetics (see valarray)
Specialization vector<bool> is defined
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16. Containers : Remarks (2)
Associative containers (maps and sets) specific member functions
operator[](k) Access to element with key k
find(k) Find element with key k
lower_bound(k) The smallest element with key k
upper_bound(k) The largest element with key k
equal_range(k) Interval of elements with key k
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17. Containers : Remarks (3)
Map
Indexing allocates the element if not already there
Map iterators point to pairs (pair<K, T>)
map<string, char> M;
M["hello"] = 'A';
map<string, char>::iterator it;
it = M.find("hello");// *it is a pair<string, char>
cout << it->first << ' ' << it->second;
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18. Containers : Remarks (4)
Multimaps, sets, multisets
Indexing allocates the element if not already there
Sets
set<K> is a sort of map<K, K>
No set operation (union, intersection…) is defined in set<K>
However, see Set Algorithms further
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19. Containers : Operation Complexity
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20. Algorithms About sixty predefined algorithms
Non-modifying operations on sequences
Modifying operations on sequences
Sort and merge operations on sequences
Set operations
Miscellaneous operations
Header file <algorithm>
 11/02/2003
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21. Algorithms on Sequences/Sets (1)
Use iterators
to specify their range of action
to retrieve the result
list<int> L;
...
list<int>::iterator it = find(L.begin(), L.end(), 7);
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22. Algorithms on Sequences/Sets (2)
May have parameters indicating an action to perform on each element of the sequence
either selecting elements
or modifying elements
list<int> L;
...
list<int>::iterator it = find(L.begin(), L.end(), 7);
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23. Algorithms on Sequences/Sets (3)
Sequence filtering
bool is_gt_4(int i) {
return i > 4; }
...
list<int> L;
int n =
count_if(L.begin(), L.end(), is_gt_4);
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24. Algorithms on Sequences/Sets (4)
Transforming a sequence
int length(string s) {
return s.size(); }
...
list<string> LS(10, ″hello ″);
vector<int> VI(LS.size());
transform(LS.begin(), LS.end(),
VI.begin(), length);
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25. Algorithms on Sequences/Sets Function-Objects (1)
Algorithms for_each, find_if, count_if... are templates functions
template <typename InputIterator, typename Predicate>
InputIterator find_if(InputIterator first,
InputIterator last,
Predicate pred) {
InputIterator it;
for (it = first; it != last && !pred(*it); it++) {}
return it; }
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26. Algorithms on Sequences/Sets Function-Objects (2)
Predicate denotes a type
either a pointer to a function (such as is_gt_4)
or a class defining operator()
In all cases the signature of the “function” should be something like
bool pred(InputIterator::value_type)
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27. Algorithms on Sequences/Sets Function-Objects (3)
A function-object is an instance of a class defining operator()
list<int> L;
class is_gt_4 {
public:
bool operator() (int i) {return i > 4;} }; …
is_gt_4 criter; // define an object
int n =
count_if(L.begin(), L.end(), criter);
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28. Algorithms on Sequences/Sets Functionals (1)
class Figure {
public:
...
void draw() const;
void rotate(int angle); };
list<Figure> LF;
for_each(LF.begin(), LF.end(), &Figure::draw);
 Error !
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29. Algorithms on Sequences/Sets Functionals (2)
for_each(LF.begin(), LF.end(),
mem_fun_ref(&Figure::draw));
mem_fun_ref is an example of a functional
here it turns a pointer to a member-function (without parameter) into a function-object
Functionals are defined in <functional>
several “special effects” : handling pointers and references, parameters passing…
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30. Algorithms on Sequences/Sets Functionals (3)
Predefined function-objects
negate<type>(p) -- p
plus<type>(p1, p2) p1 + p2 and minus, multiplies, divides, modulus
equal_to<type>(p1, p2) p1 == p2
and not_equal_to
less<type>(p1, p2) p1 < p2
and greater, less_equal, greater_equal
logical_not<type>(p) !p
logical_and<type>(p1, p2) p1 && p2
and logical_or
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31. Algorithms on Sequences/Sets Functionals (4)
Function adapters for function-objects
it = find_if(l.begin(), l.end(), bind2nd(greater<int>(), 35));
bind1st and bind2nd bind respectively the first and the second parameter of a 2 parameters function-object
not1 and not2 return the logical_not of a function-object returning a boolean (respectively with 1 or 2 parameters)
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32. Algorithms on Sequences/Sets Functionals (5)
Function adapter for ordinary functions
Function adapters can only be applied to function-objects, not to pointers to ordinary function
ptr_fun turns a pointer to a regular function into a function-object
As a consequence all the function-objects adapters can be applied to the resulting function-object
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33. Algorithms on Sequences/Sets Functionals (6)
Function adapters for member-functions
mem_fun_ref(pm)
Turn a pointer to a member-function (pm) into a function-objet: the current object is passed by reference
mem_fun(pm)
Turn a pointer to a member-function (pm) into a function-objet: the current object is passed as a pointer
Many other functionals and function-objects (see the STL documentation)
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34. Algorithms on Sequences/Sets Functionals (7)
Composing function-object adapters
list<char *> ls; … it = find_if(ls.begin(), ls.end(), bind2nd(ptr_fun(strcmp), ″hello″));
vector<Figure *> vfp; … for_each(vfp.begin(), vfp.end(), bind2nd(mem_fun(&Figure::rotate), PI/2));
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35. Algorithms Non-Modifying Operations on Sequences
for_each() Apply a function to each element
find() find_if() Find an element in a sequence with some value (resp. satisfying some condition)
find_first_of() Find an element from a sequence in another sequence
adjacent_find() Find consecutive duplicate elements
count() count_if() Count all occurrences of an element with a given value (resp. satisfying some condition)
mismatch() Find all elements differing between two sequences
equal() Check sequence equality
search() Find a sub-sequence within another sequence
find_end() Find the last occurrence of a sub-sequence within another sequence
search_n() Find the nth occurrence of a sub-sequence within another sequence
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36. Algorithms Modifying Operations on Sequences (1)
transform() Apply a function to all elements
copy() copy_backward() Copy a sequence from the beginning or the end
swap() iter_swap() Swap two elements pointed to by iterators
swap_ranges() Swap elements between two sequences
replace() replace_if() Replace elements with a given value or satisfying some condition
replace_copy() replace_copy_if() Copy a sequence, replacing elements with a given value or satisfying some condition
fill() fill_n() Replace (first n) elements by some value
generate() generate_n() Replace (first n) elements with a given value by the result of some operation
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37. Algorithms Modifying Operations on Sequences (2)
remove() remove_if() Remove elements with a given value or satisfying some condition
remove_copy() remove_copy_if() Copy a sequence, removing elements with a given value or satisfying some condition
unique() Detect and isolate consecutive duplicates
unique_copy() Copy a sequence , removing consecutive duplicates
reverse() reverse_copy() Copy a sequence in reverse order
rotate() rotate_copy() Copy a sequence together with circular permutation
random_shuffle() Permute elements according to an uniform distribution
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38. Algorithms Modifying Operations on Sequences (3)
The modifying algorithms never modify the number of elements in the container
They may modify the order of the elements
And also the value of the elements themselves
dequeue<double> dq(10, 3.14); // 10 elements
list<double> ld; // empty by default …
copy(dq.begin(), dq.end(), ld.begin());
// likely to crash!!
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39. Algorithms Modifying Operations on Sequences (4)
Insert iterators
Special iterators for which ++ (and --) do allocate new elements:
inserter, back_inserter, front_inserter
dequeue<double> dq(10, 3.14); // 10 elements
list<double> ld; // empty by default …
copy(dq.begin(), dq.end(), back_inserter(ld));
// new elements added at the end of ld
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40. Algorithms Sort/Merge Operations on Sequences
sort() stable_sort()Sort a sequence (keeping duplicate elements orders)
partial_sort() Sort the beginning of a sequence
partial_sort_copy() Copy, sort, and detect and isolate consecutive duplicates
unique_copy() Copy and sort the beginning
nth_element() Send nth element to its place
lower_bound() upper_bound() Find first (last) position of some value compatible with the order
equal_range() Find a value interval
binary_search() Find a value within a sorted sequence
merge() inplace_merge() Merge two (consecutive) sorted sequences
partition() stable_partition() Set in front (respecting relative order) elements satisfying some condition
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41. Algorithms Set Operations
includes() Check whether a sequence is a sub-sequence of another one
set_union() Build sorted union
set_intersection() Build sorted intersection
set_difference() Build sorted set of elements member of first sequence and non-member of second
set_symmetric_difference() Build sorted symmetric difference (complement of intersection within union)
These operations only work on sorted containers
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42. “Character” Strings The notion of a “character” varies
STL character strings are template classes
parameterized by the characteristics of characters, their “traits”:
representation
comparison (collating sequence)
copy operations
input-output
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43. Character Strings : basic_string
Template class
One usual specialization :
string  basic_string<char>
Usual properties :
Construction, destruction, conversion from char *
Copies (value semantics but copy on write)
Indexing ([], at) ; no substrings
Catenation (+, append…)
Comparisons…
All sequence properties, iterators, algorithms
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44. Character Strings Example: strings as sequence
Converting a character string into an array of characters
vector<char> vc;
string s = "hello, world";
copy(s.begin(), s.end(), back_inserter(vc));
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45. Input-Output Streams Type driven extensible IO system
Present in C++ nearly from the origin
Improvements in STL
Interface and semantics cleaned up
Better extensibility (manipulators)
Homogeneity with sequences (iterators)
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46. Input-Output Streams Classification by IO Medium
ios_base
ios
istream
ostream
iostream
ifstream
istringstream
ostringstream
ofstream
stringstream
fstream
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47. Input-Output Streams Stream Manipulators
Special operations
int x, y, z, t;
cout << x << flush; // flush the stream buffer
cout << x << endl; // new line and flush
cout << hex << x; // print x in hexadecimal
cout << oct << x << hex << y << dec << z;
cout << t;
// x printed in octal, y in hexadecimal,
// z in decimal, t in decimal too (last
// state of the stream)
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48. Input-Output Streams Stream Iterators
Streams, like all containers, can have iterators
vector<string> v;
copy( istream_iterator<string>(cin), istream_iterator<string>(), back_inserter(v));
copy( v.begin(), v.end(),
ostream_iterator<string>(cout, ″---″));
Note that the default constructor (istream_iterator()) corresponds to end of file
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49. Numerics Complex number (template classes) Numeric arrays : valarray
Standard operations on vectors
Sequence operations, iterators
Vector “slices”
Algorithms
Accumulation, scalar product...
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50. Header files (1) Algorithms Diagnostics Strings Containers
<vector> <list> <deque>
<queue> <stack> <map>
<set> <bitset>
General utilities
<utility> <functional>
<memory> <ctime>
Iterators
<iterator>
Algorithms
<algorithm> <cstdlib>
Diagnostics
<stdexcept> <cassert>
<cerrno>
Strings
<string> <cctype>
<cwtype> <cstring>
<cwstring> <cstdlib>
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51. Header files (2) Input-output Localization Run-time support Numerics
<iosfwd> <iostream>
<ios> <streambuf>
<istream> <ostream>
<iomanip> <sstream>
<cstdlib> <fstream>
<cstdio> <cwchar>
Localization
<locale> <clocale>
Run-time support
<limits> <climits>
<cfloat> <new>
<typeinfo> <exception>
<cstddef> <cstdarg>
<csetjmp> <cstdlib>
<ctime> <csignal>
Numerics
<complex> <valarray>
<numerics> <cmath>
<cstdlib>
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52. References And many others… Bjarne Stroustrup
The C++ Programming Language, 3rd Edition
Addison-Wesley, 1997
Nicolai M. Josuttis
The C++ Standard Library: A Tutorial and Reference
Addison-Wesley, 1999
Scott Meyers
Effective STL
Addison-Wesley, 2001
And many others…
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