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map(3C++)			       -			     map(3C++)

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

NAME
       map

	-  An associative container with access to non-key values using unique
       keys. A map supports bidirectional iterators.

SYNOPSIS
       #include <map>
       template <class Key, class T, class Compare = less<Key>
	 class Allocator = allocator<pair<const Key, T>> >
class map;

DESCRIPTION
       map_<Key,_T,_Compare,_Allocator> gives fast access to stored values  of
       type  T that are indexed by unique keys of type Key. The default opera‐
       tion for key comparison is the < operator.

       map has bidirectional iterators that point to an instance of pair<const
       Key  x,	T  y>  where x is the key and y is the stored value associated
       with that key. The definition of map includes a typedef	to  this  pair
       called value_type.

       The  types used for both the template parameters Key and T 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 T, class Compare = less<Key>
	 class Allocator = allocator<pair<const Key, T>> >
class map {

public:

// types

  typedef Key key_type;
  typedef typename Allocator::pointer pointer;
  typedef typename Allocator::const_pointer const_pointer;
  typedef T mapped_type;
  typedef pair<const Key, T> value_type;
  typedef Compare key_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;

  class value_compare
      : public binary_function<value_type, value_type, bool>
   {
    friend class map<Key, T, Compare, Allocator>;

    protected :
      Compare comp;
      value_compare(Compare c): comp(c) {}
    public :
      bool operator() (const value_type&,
		       const value_type&) const;
   };

// Construct/Copy/Destroy

  explicit map (const Compare& = Compare(),
		const Allocator& = Allocator ());
  template <class InputIterator>
   map (InputIterator, InputIterator,
	const Compare& = Compare(),
	const Allocator& = Allocator ());
  map (const map<Key, T, Compare, Allocator>&);
   ~map();
  map<Key, T, Compare, Allocator>&
   operator= (const map<Key, T, 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;

// Element Access

  mapped_type& operator[] (const key_type&);

// 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 (map<Key, T, Compare, Allocator>&);
  void clear();

// Observers

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

// Map operations

  iterator find (const key_value&);
  const_iterator find (const key_value&) const;
  size_type count (const key_type&) const;
  iterator lower_bound (const key_type&);
  const_iterator lower_bound (const key_type&) const;
  iterator upper_bound (const key_type&);
  const_iterator upper_bound (const key_type&) const;
  pair<iterator, iterator> equal_range (const key_type&);
  pair<const_iterator, const_iterator>
    equal_range (const key_type&) const;
};

// Non-member Map Operators

template <;class Key, class T, class Compare, class Allocator>
 bool operator== (const map<Key, T, Compare, Allocator>&,
		 const map<Key, T, Compare, Allocator>&);

template <;class Key, class T, class Compare, class Allocator>
 bool operator!= (const map<Key, T, Compare, Allocator>&,
		 const map<Key, T, Compare, Allocator>&);

template <;class Key, class T, class Compare, class Allocator>
bool operator<; (const map<Key, T, Compare, Allocator>&,
		const map<Key, T, Compare, Allocator>&);

template <;class Key, class T, class Compare, class Allocator>
bool operator> (const map<Key, T, Compare, Allocator>&,
		const map<Key, T, Compare, Allocator>&);

template <;class Key, class T, class Compare, class Allocator>
bool operator<;= (const map<Key, T, Compare, Allocator>&,
		const map<Key, T, Compare, Allocator>&);

template <;class Key, class T, class Compare, class Allocator>
bool operator>= (const map<Key, T, Compare, Allocator>&,
		const map<Key, T, Compare, Allocator>&);

// Specialized Algorithms

template <;class Key, class T, class Compare, class Allocator>
void swap (map<;*Key,T,Compare,Allocator>&,
	   map<Key,T,Compare,Allocator>&);

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

   Constructs an empty map that uses the relation comp to order keys, if it is
   supplied. The map uses the allocator alloc for all storage management.

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

   Constructs  a map containing values in the range [first, last). Creation of
   the new map is only guaranteed to succeed if the iterators first  and  last
   return  values of type pair<class Key,	class Value> and all values of
   Key in the range[first, last) are unique. The map uses the relation comp to
   order keys, and the allocator alloc for all storage management.

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

   Creates a new map by copying all pairs of key and value from x.

DESTRUCTORS
       ~map();

   Releases any allocated memory for this map.

ALLOCATORS
       allocator_type get_allocator() const;

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

ITERATORS
       iterator
       begin();

   Returns  an	iterator  pointing  to	the  first  element stored in the map.
   "First" is defined by the map's comparison operator, Compare.

const_iterator
begin() const;

   Returns a const_iterator pointing to the first element stored in the map.

iterator
end();

   Returns an iterator pointing to the last element  stored  in	 the  map  (in
   other words, the off-the-end value).

const_iterator
end() const;

   Returns a const_iterator pointing to the last element stored in the map.

reverse_iterator
rbegin();

   Returns a reverse_iterator pointing to the first element stored in the map.
   "First" is defined by the map's comparison operator, Compare.

const_reverse_iterator
rbegin() const;

   Returns a const_reverse_iterator pointing to the first  element  stored  in
   the map.

reverse_iterator
rend();

   Returns  a  reverse_iterator pointing to the last element stored in the map
   (in other words, the off-the-end value).

const_reverse_iterator
rend() const;

   Returns a const_reverse_iterator pointing to the last element stored in the
   map.

MEMBER OPERATORS
       map<Key, T, Compare, Allocator>&
       operator=(const map<Key, T, Compare, Allocator>& x);

   Replaces the contents of *this with a copy of the map x.

mapped_type&
operator[](const key_type& x);

   If  an  element  with  the key x exists in the map, then a reference to its
   associated value is returned. Otherwise the pair x,T() is inserted into the
   map and a reference to the default object T() is returned.

MEMBER FUNCTIONS
       void
       clear();

   Erases all elements from the self.

size_type
count(const key_type& x) const;

   Returns  a 1 if a value with the key x exists in the map. Otherwise returns
   a 0.

bool
empty() const;

   Returns true if the map is empty, false otherwise.

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

   Returns the pair (lower_bound(x), upper_bound(x)).

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

   Returns the pair (lower_bound(x), upper_bound(x)).

void
erase(iterator position);

   Deletes the map element pointed to by the iterator position.

void
erase(iterator first, iterator last);

   If the iterators first and last point to the same map and last is reachable
   from	 first,	 all  elements in the range (first, last) are deleted from the
   map. Returns an iterator pointing to the element following the last deleted
   element, or end() if there were no elements after the deleted range.

size_type
erase(const key_type& x);

   Deletes  the	 element  with	the  key  value x from the map, if one exists.
   Returns 1 if x existed in the map, 0 otherwise.

iterator
find(const key_type& x);

   Searches the map for a pair with the key value x and returns an iterator to
   that	 pair  if  it is found. If such a pair is not found the value end() is
   returned.

const_iterator find(const key_type& x) const;

   Same as find above but returns a const_iterator.

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

   If a value_type with the same key as x is not present in the map, then x is
   inserted  into the map. Otherwise, the pair is not inserted. A position may
   be supplied as a hint regarding where to do the insertion. If the insertion
   is done right after position, then it takes amortized constant time. Other‐
   wise it takes O(log N) time.

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

   Copies of each element in the range [first, last) that possess a unique key
   (one not already in the map) are inserted into the map. The iterators first
   and last must return values	of  type  pair<T1,T2>.	This  operation	 takes
   approximately O(N*log(size()+N)) time.

key_compare
key_comp() const;

   Returns a function object capable of comparing key values using the compar‐
   ison operation, Compare, of the current map.

iterator
lower_bound(const key_type& x);

   Returns a reference to the first entry with a key greater than or equal  to
   x.

const_iterator
lower_bound(const key_type& x) const;

   Same as lower_bound above but returns a const_iterator.

size_type
max_size() const;

   Returns  the	 maximum  possible  size  of the map.	This size is only con‐
   strained by the number of unique keys that can be represented by  the  type
   Key.

size_type
size() const;

   Returns the number of elements in the map.

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

   Swaps the contents of the map x with the current map, *this.

iterator
upper_bound(const key_type& x);

   Returns a reference to the first entry with a key less than or equal to x.

const_iterator
upper_bound(const key_type& x) const;

   Same as upper_bound above but returns a const_iterator.

value_compare
value_comp() const;

   Returns  a  function	 object capable of comparing pair<const Key, T> values
   using the comparison operation, Compare, of the current map. This  function
   is identical to key_comp for sets.

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

   Returns true if all elements in x are element-wise equal to all elements in
   y, using (T::operator==). Otherwise it returns false.

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

   Returns !(x==y).

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

   Returns true if x is lexicographically less than y. Otherwise,  it  returns
   false.

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

   Returns y < x.

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

   Returns !(y < x).

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

   Returns !(x < y).

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

   Swaps the contents of a and b.

EXAMPLE
//
// map.cpp
//
 #include <string>
 #include <map>
 #include <iostream>
using namespace std;

typedef map<;string, int, less<string> > months_type;

 // Print out a pair
template <;class First, class Second>
ostream& operator<;<(ostream& out,
		    const pair<First,Second> & p)
 {
  cout << p.first << " has " << p.second << " days";
  return out;
 }

 // Print out a map
ostream& operator<;<(ostream& out, const months_type & l)
 {
  copy(l.begin(),l.end(), ostream_iterator
		<months_type::value_type,char>(cout,"\n"));
  return out;
 }

int main(void)
 {
   // create a map of months and the number of days
   // in the month
  months_type months;

  typedef months_type::value_type value_type;

   // Put the months in the multimap
  months.insert(value_type(string("January"),	31));
  months.insert(value_type(string("February"),	 28));
  months.insert(value_type(string("February"),	 29));
  months.insert(value_type(string("March"),	31));
  months.insert(value_type(string("April"),	30));
  months.insert(value_type(string("May"),	31));
  months.insert(value_type(string("June"),	30));
  months.insert(value_type(string("July"),	31));
  months.insert(value_type(string("August"),	31));
  months.insert(value_type(string("September"), 30));
  months.insert(value_type(string("October"),	31));
  months.insert(value_type(string("November"),	30));
  months.insert(value_type(string("December"),	31));

   // print out the months
   // Second February is not present
  cout << months << endl;

   // Find the Number of days in June
  months_type::iterator p = months.find(string("June"));

   // print out the number of days in June
  if (p != months.end())
    cout << endl << *p << endl;

  return 0;
 }

Program Output

April has 30 days
August has 31 days
December has 31 days
February has 28 days
January has 31 days
July has 31 days
June has 30 days
March has 31 days
May has 31 days
November has 30 days
October has 31 days
September has 30 days

WARNINGS
       Member  function	 templates  are used in all containers included in the
       Standard Template Library. An example of this feature is the  construc‐
       tor  for map<Key,T,Compare,Allocator> that takes two templatized itera‐
       tors:

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

map also has an insert function	 of  this  type.  These	 functions,  when  not
restricted  by compiler limitations, allow you to use any type of input itera‐
tor as arguments. For compilers that do not support this  feature,  substitute
functions  allow  you  to  use an iterator obtained from the same type of container as the one you are constructing (or calling 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 function templates, you
can construct a map in the following two ways:

map<;int, int, less<int> >::value_type intarray[10];
map<;int, int, less<int> > first_map(intarray,
				   intarray + 10);
map<;int, int, less<int> > second_map(first_map.begin(),
				    first_map.end());

But not this way:

map<;long, long, less<long> > long_map(first_map.begin(),
				     first_map.end());

Since the long_map and first_map are not the same type.

Also, many compilers do not support default template arguments. If  your  com‐
piler is one of these, you always need to supply the Compare template argument
and the Allocator template argument. For instance, you have to write:

map<;int, int, less<int>, allocator<int> >

instead of:

map<;int, int>

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

SEE ALSO
       allocator, Containers, Iterators, multimap

Rogue Wave Software		  02 Apr 1998			     map(3C++)
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