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                       Standard C++ Library
             Copyright 1998, Rogue Wave Software, Inc.


NAME
     set

      - An associative container that supports unique keys. A set
     supports bidirectional iterators.



SYNOPSIS
     #include <set>
     template <class Key, class Compare = less<Key>,
     class Allocator = allocator<Key> >
     class set ;



DESCRIPTION
     set<Key,_Compare,_Allocator>_is  an  associative   container
     that  supports  unique keys and allows for fast retrieval of
     the keys. A set contains, at most, one of any key value. The
     keys are sorted using Compare.

     Since a set maintains a total order  on  its  elements,  you
     cannot  alter  the  key  values  directly. Instead, you must
     insert new elements with an insert_iterator.

     Any type used for the template parameter  Key  must  include
     the  following (where T is the type, t is a value of T and u
     is a const value of T):

     Copy constructors   T(t) and T(u)



     Destructor   t.~T()



     Address of   &t and &u yielding T* and const T* respectively



     Assignment   t = a where a is a (possibly const) value of T



     The type  used  for  the  Compare  template  parameter  must
     satisfy the requirements for binary functions.



INTERFACE
     template <class Key, class Compare = less<Key>,
     class Allocator = allocator<Key> >
     class set {
     public:
     // types
     typedef Key key_type;
     typedef Key value_type;
     typedef Compare key_compare;
     typedef Compare value_compare;
     typedef Allocator allocator_type;
     typedef typename Allocator::reference reference;
     typedef typename Allocator::const_reference const_reference;
     class iterator;
     class const_iterator;
     typedef typename Allocator::size_type size_type;
     typedef typename Allocator::difference_type difference_type;
     typedef typename std::reverse_iterator<iterator>
                          reverse_iterator;
     typedef typename std::reverse_iterator<const_iterator>
                          const_reverse_iterator;

     // Construct/Copy/Destroy
     explicit set (const Compare& = Compare(),
                  const Allocator& = Allocator ());
     template <class InputIterator>
     set (InputIterator, InputIterator,
         const Compare& = Compare(),
         const Allocator& = Allocator ());
     set (const set<Key, Compare, Allocator>&);
     ~set ();
     set<Key, Compare, Allocator>& operator=
        (const set <Key, Compare, Allocator>&);
     allocator_type get_allocator () const;

     // Iterators
     iterator begin ();
     const_iterator begin () const;
     iterator end ();
     const_iterator end () const;
     reverse_iterator rbegin ();
     const_reverse_iterator rbegin () const;
     reverse_iterator rend ();
     const_reverse_iterator rend () const;

     // Capacity
     bool empty () const;
     size_type size () const;
     size_type max_size () const;

     // Modifiers
     pair<iterator, bool> insert (const value_type&);
     iterator insert (iterator, const value_type&);
     template <class InputIterator>
     void insert (InputIterator, InputIterator);
     void erase (iterator);
     size_type erase (const key_type&);
     void erase (iterator, iterator);
     void swap (set<Key, Compare, Allocator>&);
     void clear ();


     // Observers
     key_compare key_comp () const;
     value_compare value_comp () const;

     // Set operations
     size_type count (const key_type&) const;
     pair<iterator,  iterator>  equal_range  (const    key_type&)
     const;
     iterator find (const key_type&) const;
     iterator lower_bound (const key_type&) const;
     iterator upper_bound (const key_type&) const
     };

     // Non-member Operators
     template <class Key, class Compare, class Allocator>
     bool operator== (const set<Key, Compare, Allocator>&,
     const set<Key, Compare, Allocator>&);
     template <class Key, class Compare, class Allocator>
     bool operator!= (const set<Key, Compare, Allocator>&,
     const set<Key, Compare, Allocator>&);
     template <class Key, class Compare, class Allocator>
     bool operator< (const set<Key, Compare, Allocator>&,
     const set<Key, Compare, Allocator>&);
     template <class Key, class Compare, class Allocator>
     bool operator> (const set<Key, Compare, Allocator>&,
     const set<Key, Compare, Allocator>&);
     template <class Key, class Compare, class Allocator>
     bool operator<= (const set<Key, Compare, Allocator>&,
     const set<Key, Compare, Allocator>&);
     template <class Key, class Compare, class Allocator>
     bool operator>= (const set<Key, Compare, Allocator>&,
     const set<Key, Compare, Allocator>&);

     // Specialized Algorithms
     template <class Key, class Compare, class Allocator>
     void swap (set <Key, Compare, Allocator>&,
     set <Key, Compare, Allocator>&);



CONSTRUCTORS
     explicit
     set(const Compare& comp = Compare(),
     const Allocator& alloc = Allocator());


        Creates a set of zero elements. If  the  function  object
        comp  is  supplied, it is used to compare elements of the
        set.   Otherwise, the default function object in the tem-
        plate argument is used. The template argument defaults to
        less (<). The allocator alloc is  used  for  all  storage
        management.



     template <class InputIterator>
     set(InputIterator first, InputIterator last,
     const Compare& comp = Compare()
     const Allocator& alloc = Allocator());


        Creates a set of length last -  first,  filled  with  all
        values  obtained  by  dereferencing the InputIterators on
        the range [first, last). If the function object  comp  is
        supplied, it is used to compare elements of the set. Oth-
        erwise, the default function object in the template argu-
        ment is used. The template argument defaults to less (<).
        Uses the allocator Allocator() for  all  storage  manage-
        ment.



     set(const set<Key, Compare, Allocator>& x);


        Copy constructor. Creates a copy of x.



DESTRUCTORS
     ~set();


        Releases any allocated memory for self.

ASSIGNMENT OPERATORS
     set<Key, Compare, Allocator>&
     operator=(const set<Key, Compare, Allocator>& x);


        Returns a reference to self. Self shares  an  implementa-
        tion with x.



ALLOCATORS
     allocator_type
     get_allocator() const;


        Returns a copy of the allocator used by self for  storage
        management.



ITERATORS
     iterator
     begin();


        Returns an iterator that points to the first  element  in
        self.



     const_iterator
     begin() const;


        Returns a const_iterator that points to the first element
        in self.



     iterator
     end();


        Returns an  iterator  that  points  to  the  past-the-end
        value.



     const_iterator
     end() const;


        Returns a const_iterator that points to the  past-the-end
        value.



     reverse_iterator
     rbegin();


        Returns a reverse_iterator that points to  the  past-the-
        end value.



     const_reverse_iterator
     rbegin() const;


        Returns  a  const_reverse_iterator  that  points  to  the
        past-the-end value.



     reverse_iterator
     rend();


        Returns a reverse_iterator that points to the first  ele-
        ment.



     const_reverse_iterator
     rend() const;


        Returns a const_reverse_iterator that points to the first
        element.



MEMBER FUNCTIONS
     void
     clear();


        Erases all elements from the set.



     size_type
     count(const key_type& x) const;


        Returns the number of elements equal to x.  Since  a  set
        supports unique keys, count always returns 1 or 0.



     bool
     empty() const;


        Returns true if the size is zero.



     pair<iterator, iterator>
     equal_range(const key_type&  x) const;


        Returns     pair(lower_bound(x),upper_bound(x)).      The
        equal_range function indicates the valid range for inser-
        tion of x into the set.



     size_type
     erase(const key_type& x);


        Deletes all the elements matching x.   Returns the number
        of  elements  erased.  Since  a set supports unique keys,
        erase always returns 1 or 0.



     void
     erase(iterator position);


        Deletes the map element pointed to by the iterator  posi-
        tion. Returns an iterator pointing to the element follow-
        ing the deleted element, or end() if the deleted item was
        the last one in this list.



     void
     erase(iterator first, iterator last);


        Deletes the elements in the range (first, last).  Returns
        an  iterator  pointing  to the element following the last
        deleted element, or end() if there were no elements after
        the deleted range.



     iterator
     find(const key_value& x) const;


        Returns an iterator that points to the element  equal  to
        x.  If  there  is no such element, the iterator points to
        the past-the-end value.



     pair<iterator, bool>
     insert(const value_type& x);


        Inserts x into self according to the comparison  function
        object. The template's default comparison function object
        is less (<). If the insertion succeeds, it returns a pair
        composed  of  the  iterator  position where the insertion
        took place and true. Otherwise, the pair contains the end
        value and false.



     iterator
     insert(iterator position, const value_type& x);


        x is inserted into the set. A position may be supplied as
        a hint regarding where to do the insertion. If the inser-
        tion is done right after position, then  it  takes  amor-
        tized  constant  time. Otherwise it takes 0 (log N) time.
        The return value points to the inserted x.



     template <class InputIterator>
     void
     insert(InputIterator first, InputIterator last);


        Inserts copies of  the  elements  in  the  range  [first,
        last].



     key_compare
     key_comp() const;


        Returns the comparison function object for the set.



     iterator
     lower_bound(const key_type& x) const;


        Returns an iterator that points to the first element that
        is  greater  than or equal to x. If there is no such ele-
        ment, the iterator points to the past-the-end value.



     size_type
     max_size() const;


        Returns the size of the largest possible set.



     size_type
     size() const;


        Returns the number of elements.



     void
     swap(set<Key, Compare, Allocator>& x);


        Exchanges self with x.



     iterator
     upper_bound(const key_type& x) const


        Returns an iterator that points to the first element that
        is  greater  than  or  equal  to  x.  If there is no such
        element, the iterator points to the past-the-end value.



     value_compare
     value_comp() const;


        Returns the set's comparison object. This is identical to
        the function key_comp().



NON-MEMBER OPERATORS
     template <class Key, class Compare, class Allocator>
     bool operator==(const set<Key, Compare, Allocator>& x,
     const set<Key, Compare, Allocator>& y);


        Returns true if x is the same as y.



     template <class Key, class Compare, class Allocator>
     bool operator!=(const set<Key, Compare, Allocator>& x,
     const set<Key, Compare, Allocator>& y);


        Returns !(x==y).



     template <class Key, class Compare, class Allocator>
     bool operator<(const set <Key, Compare, Allocator>& x,
     const set <Key, Compare, Allocator>& y);


        Returns true if the elements contained in x  are  lexico-
        graphically less than the elements contained in y.



     template <class Key, class Compare, class Allocator>
     bool operator>(const set <Key, Compare, Allocator>& x,
     const set <Key, Compare, Allocator>& y);


        Returns y < x.


     template <class Key, class Compare, class Allocator>
     bool operator<=(const set <Key, Compare, Allocator>& x,
     const set <Key, Compare, Allocator>& y);


        Returns !(y < x).



     template <class Key, class Compare, class Allocator>
     bool operator>=(const set <Key, Compare, Allocator>& x,
     const set <Key, Compare, Allocator>& y);


        Returns !(x < y).



SPECIALIZED ALGORITHMS
     template <class Key, class Compare, class Allocator>
     void swap(set <Key, Compare, Allocator>& a,
     set <Key, Compare, Allocator>& b);


        Swaps the contents of a and b.



EXAMPLE
     //
     // setex.cpp
     //
     #include <set>
     #include <iostream>
     using namespace std;

     typedef set<double, less<double>, allocator<double> >
            set_type;
     ostream& operator<<(ostream& out, const set_type& s)
      {
     copy(s.begin(), s.end(),
         ostream_iterator<set_type::value_type,char>(cout," "));
     return out;
      }

     int main(void)
      {
     // create a set of doubles
       set_type   sd;
       int         i;

     for(i = 0; i < 10; ++i) {
     // insert values
     sd.insert(i);
        }

     // print out the set
     cout << sd << endl << endl;

     // now let's erase half of the elements in the set
     int half = sd.size() >> 1;
     set_type::iterator sdi = sd.begin();
     advance(sdi,half);
     sd.erase(sd.begin(),sdi);
     // print it out again
     cout << sd << endl << endl;

     // Make another set and an empty result set
     set_type sd2, sdResult;
     for (i = 1; i < 9; i++)
      sd2.insert(i+5);
     cout << sd2 << endl;
     // Try a couple of set algorithms
     set_union(sd.begin(),sd.end(),sd2.begin(),sd2.end(),
              inserter(sdResult,sdResult.begin()));
     cout << "Union:" << endl << sdResult << endl;
     sdResult.erase(sdResult.begin(),sdResult.end());
     set_intersection(sd.begin(),sd.end(),
                     sd2.begin(),sd2.end(),
                     inserter(sdResult,sdResult.begin()));
     cout << "Intersection:" << endl << sdResult << endl;
     return 0;
      }

     Program Output



     0 1 2 3 4 5 6 7 8 9

     5 6 7 8 9

     6 7 8 9 10 11 12 13
     Union:
     5 6 7 8 9 10 11 12 13
     Intersection:
     6 7 8 9


WARNINGS
     Member  function  templates  are  used  in  all   containers
     included  in  the  Standard  Template Library. An example of
     this feature is the constructor for set <Key, Compare, Allo-
     cator> that takes two templatized iterators:


     template <class InputIterator>
     set (InputIterator, InputIterator,
     const Compare& = Compare(),
     const Allocator& = Allocator());

     set also has an insert function of this  type.  These  func-
     tions,  when  not  restricted by compiler limitations, allow
     you to use any type of input iterator  as  arguments.    For
     compilers that do not support this feature, substitute func-
     tions allow you to use an iterator obtained  from  the  same
     type  of  container as the one you are constructing (or cal-
     ling a member function on), or you can use a pointer to  the
     type of element you have in the container.

     For example, if your compiler does not support member  func-
     tion templates, you can construct a set in the following two
     ways:


     int intarray[10];
     set<int> first_set(intarray, intarray + 10);
     set<int> second_set(first_set.begin(),
     first_set.end());

     but not this way:


     set<long> long_set(first_set.begin(),
     first_set.end());

     since the long_set and first_set are not the same type.

     Also, many compilers do not support default  template  argu-
     ments.  If  your compiler is one of these you always need to
     supply the Compare template argument and the Allocator  tem-
     plate argument. For instance, you need to write:

     set<int, less<int>, allocator<int> >

     instead of:

     set<int>

     If your compiler does not support namespaces,  then  you  do
     not need the using declaration for std.

SEE ALSO
     allocator,       Bidirectional_Iterators,        Containers,
     lexicographical_compare

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