hash_map.html

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<A HREF="#hash traits">hash traits</A> object of type <CODE>Tr</CODE>.
You access this stored object by calling the member function
<CODE><A HREF="#hash_map::key_comp">key_comp</A>()</CODE>.
Such a traits object must behave the same as an object of class
<CODE><A HREF="#hash_compare">hash_compare</A>&lt;Key, Pr&gt;</CODE>.
Specifically, for all values <CODE>keyval</CODE> of type <CODE>Key</CODE>,
the call <CODE>key_comp()(keyval)</CODE> yields a distribution
of values of type <CODE>size_t</CODE>.
Moreover, class <CODE>Pr</CODE> imposes a
<A HREF="lib_stl.html#strict weak ordering">strict weak ordering</A>
on sort keys of type <CODE>Key</CODE>.
For any element <CODE>X</CODE> that precedes
<CODE>Y</CODE> in the sequence and has the same hash value,
<CODE>key_comp()(Y.<A HREF="utility.html#pair::first">first</A>,
X.first)</CODE> is false. (For the default function object
<CODE><A HREF="functio2.html#less">less</A>&lt;Key&gt;</CODE>,
sort keys never decrease in value.)
Unlike template class <CODE><A HREF="#hash_multimap">hash_multimap</A></CODE>,
an object of template class <CODE>hash_map</CODE> ensures that
<CODE>key_comp()(X.first, Y.first)</CODE> is true.
(Each key is unique.)</P>

<P>The actual order of elements in the controlled sequence depends on the
hash function, the ordering function, and the current size of the hash
table stored in the container object. You cannot determine the current size
of the hash table, so you cannot in general predict the order of elements
in the controlled sequence.</P>

<P>The object allocates and frees storage for the sequence it controls
through a stored <A HREF="memory.html#allocator object">allocator object</A>
of class <CODE>Alloc</CODE>. Such an allocator object must have
the same external interface as an object of template class
<A HREF="memory.html#allocator"><CODE>allocator</CODE></A>.
Note that the stored allocator object is <I>not</I> copied when the container
object is assigned.</P>

<H3><CODE><A NAME="hash_map::allocator_type">hash_map::allocator_type</A></CODE></H3>

<PRE>typedef Alloc <B>allocator_type</B>;</PRE>

<P>The type is a synonym for the template parameter <CODE>Alloc</CODE>.</P>

<H3><CODE><A NAME="hash_map::begin">hash_map::begin</A></CODE></H3>

<PRE>const_iterator <B>begin</B>() const;
iterator <B>begin</B>();</PRE>

<P>The member function returns a bidirectional iterator that points at
the first element of the sequence (or just beyond the end of an empty
sequence).</P>

<H3><CODE><A NAME="hash_map::clear">hash_map::clear</A></CODE></H3>

<PRE>void <B>clear</B>();</PRE>

<P>The member function calls
<CODE><A HREF="#hash_map::erase">erase</A>(
<A HREF="#hash_map::begin">begin</A>(),
<A HREF="#hash_map::end">end</A>())</CODE>.</P>

<H3><CODE><A NAME="hash_map::const_iterator">hash_map::const_iterator</A></CODE></H3>

<PRE>typedef T1 <B>const_iterator</B>;</PRE>

<P>The type describes an object that can serve as a constant
bidirectional iterator for the controlled sequence.
It is described here as a
synonym for the implementation-defined type <CODE>T1</CODE>.</P>

<H3><CODE><A NAME="hash_map::const_pointer">hash_map::const_pointer</A></CODE></H3>

<PRE>typedef Alloc::const_pointer <B>const_pointer</B>;</PRE>

<P>The type describes an object that can serve as a constant pointer
to an element of the controlled sequence.</P>

<H3><CODE><A NAME="hash_map::const_reference">hash_map::const_reference</A></CODE></H3>

<PRE>typedef Alloc::const_reference <B>const_reference</B>;</PRE>

<P>The type describes an object that can serve as a constant reference
to an element of the controlled sequence.</P>

<H3><CODE><A NAME="hash_map::const_reverse_iterator">hash_map::const_reverse_iterator</A></CODE></H3>

<PRE>typedef reverse_iterator&lt;const_iterator&gt;
    <B>const_reverse_iterator</B>;</PRE>

<P>The type describes an object that can serve as a constant reverse
bidirectional iterator for the controlled sequence.</P>

<H3><CODE><A NAME="hash_map::count">hash_map::count</A></CODE></H3>

<PRE>size_type <B>count</B>(const Key&amp; keyval) const;</PRE>

<P>The member function returns the number of elements in the range
<CODE>[<A HREF="#hash_map::lower_bound">lower_bound</A>(keyval),
<A HREF="#hash_map::upper_bound">upper_bound</A>(keyval)).</CODE></P>

<H3><CODE><A NAME="hash_map::difference_type">hash_map::difference_type</A></CODE></H3>

<PRE>typedef T3 <B>difference_type</B>;</PRE>

<P>The signed integer type describes an object that can represent the
difference between the addresses of any two elements in the controlled
sequence. It is described here as a
synonym for the implementation-defined type <CODE>T3</CODE>.</P>

<H3><CODE><A NAME="hash_map::empty">hash_map::empty</A></CODE></H3>

<PRE>bool <B>empty</B>() const;</PRE>

<P>The member function returns true for an empty controlled sequence.</P>

<H3><CODE><A NAME="hash_map::end">hash_map::end</A></CODE></H3>

<PRE>const_iterator <B>end</B>() const;
iterator <B>end</B>();</PRE>

<P>The member function returns a bidirectional iterator that points
just beyond the end of the sequence.</P>

<H3><CODE><A NAME="hash_map::equal_range">hash_map::equal_range</A></CODE></H3>

<PRE>pair&lt;iterator, iterator&gt; <B>equal_range</B>(const Key&amp; keyval);
pair&lt;const_iterator, const_iterator&gt;
    <B>equal_range</B>(const Key&amp; keyval) const;</PRE>

<P>The member function returns a pair of iterators <CODE>X</CODE>
such that <CODE>X.<A HREF="utility.html#pair::first">first</A> ==
<A HREF="#hash_map::lower_bound">lower_bound</A>(keyval)</CODE>
and <CODE>X.<A HREF="utility.html#pair::second">second</A> ==
<A HREF="#hash_map::upper_bound">upper_bound</A>(keyval)</CODE>.</P>

<H3><CODE><A NAME="hash_map::erase">hash_map::erase</A></CODE></H3>

<PRE>iterator <B>erase</B>(iterator where);
iterator <B>erase</B>(iterator first, iterator last);
size_type <B>erase</B>(const Key&amp; keyval);</PRE>

<P>The first member function removes the element of the controlled
sequence pointed to by <CODE>where</CODE>.
The second member function removes the elements
in the interval <CODE>[first, last)</CODE>.
Both return an iterator that designates the first element remaining
beyond any elements removed, or
<CODE><A HREF="#hash_map::end">end</A>()</CODE> if no such element exists.</P>

<P>The third member function removes
the elements with sort keys in the range
<CODE>[<A HREF="#hash_map::lower_bound">lower_bound</A>(keyval),
<A HREF="#hash_map::upper_bound">upper_bound</A>(keyval)).</CODE>
It returns the number of elements it removes.</P>

<P>The member functions never throw an exception.</P>

<H3><CODE><A NAME="hash_map::find">hash_map::find</A></CODE></H3>

<PRE>iterator <B>find</B>(const Key&amp; keyval);
const_iterator <B>find</B>(const Key&amp; keyval) const;</PRE>

<P>The member function returns
<CODE><A HREF="#hash_map::lower_bound">lower_bound</A>(keyval)</CODE>.</P>

<H3><CODE><A NAME="hash_map::get_allocator">hash_map::get_allocator</A></CODE></H3>

<PRE>Alloc <B>get_allocator</B>() const;</PRE>

<P>The member function returns the stored
<A HREF="memory.html#allocator object">allocator object</A>.</P>

<H3><CODE><A NAME="hash_map::hash_map">hash_map::hash_map</A></CODE></H3>

<PRE><B>hash_map</B>();
explicit <B>hash_map</B>(const Tr&amp; traits);
<B>hash_map</B>(const Tr&amp; traits, const Alloc&amp; al);
<B>hash_map</B>(const hash_map&amp; right);
template&lt;class InIt&gt;
    <B>hash_map</B>(InIt first, InIt last);
template&lt;class InIt&gt;
    <B>hash_map</B>(InIt first, InIt last,
        const Tr&amp; traits);
template&lt;class InIt&gt;
    <B>hash_map</B>(InIt first, InIt last,
        const Tr&amp; traits, const Alloc&amp; al);</PRE>

<P>All constructors store an
<A HREF="memory.html#allocator object">allocator object</A> and
initialize the controlled sequence. The allocator object is the argument
<CODE>al</CODE>, if present. For the copy constructor, it is
<CODE>right.<A HREF="#hash_map::get_allocator">get_allocator</A>()</CODE>.
Otherwise, it is <CODE>Alloc()</CODE>.</P>

<P>All constructors also store a
<A HREF="#hash traits">hash traits</A> object that can later
be returned by calling
<CODE><A HREF="#hash_map::key_comp">key_comp</A>()</CODE>.
The hash traits object is the argument <CODE>traits</CODE>, if present.
For the copy constructor, it is
<CODE>right.<A HREF="#hash_map::key_comp">key_comp</A>()</CODE>).
Otherwise, it is <CODE>Tr()</CODE>.</P>

<P>The first three constructors specify an
empty initial controlled sequence. The fourth constructor specifies
a copy of the sequence controlled by <CODE>right</CODE>.
The last three constructors specify the sequence of element values
<CODE>[first, last)</CODE>.</P>


<H3><CODE><A NAME="hash_map::insert">hash_map::insert</A></CODE></H3>

<PRE>pair&lt;iterator, bool&gt; <B>insert</B>(const value_type&amp; val);
iterator <B>insert</B>(iterator where, const value_type&amp; val);
template&lt;class InIt&gt;
    void <B>insert</B>(InIt first, InIt last);</PRE>

<P>The first member function determines whether an element <CODE>X</CODE>
exists in the sequence whose key has
<A HREF="lib_stl.html#equivalent ordering">equivalent ordering</A>
to that of <CODE>val</CODE>. If not, it creates such
an element <CODE>X</CODE> and initializes it with <CODE>val</CODE>.
The function then determines the iterator <CODE>where</CODE> that
designates <CODE>X</CODE>. If an insertion occurred, the function
returns <CODE><A HREF="utility.html#pair">pair</A>(iter, true)</CODE>.
Otherwise, it returns <CODE>pair(where, false)</CODE>.</P>

<P>The second member function returns <CODE>insert(val).first</CODE>,
using <CODE>where</CODE> as a starting place within the controlled
sequence to search for the insertion point. (Insertion can
possibly occur somewhat faster, if the
insertion point immediately precedes or follows <CODE>where</CODE>.)
The third member function
inserts the sequence of element values,
for each <CODE>where</CODE> in the range <CODE>[first, last)</CODE>,
by calling <CODE>insert(*where)</CODE>.</P>


<P>If an exception is thrown during the
insertion of a single element, the container is left unaltered
and the exception is rethrown.
If an exception is thrown during the
insertion of multiple elements, the container is left in a stable
but unspecified state and the exception is rethrown.</P>

<H3><CODE><A NAME="hash_map::iterator">hash_map::iterator</A></CODE></H3>

<PRE>typedef T0 <B>iterator</B>;</PRE>

<P>The type describes an object that can serve as a bidirectional
iterator for the controlled sequence.
It is described here as a
synonym for the implementation-defined type <CODE>T0</CODE>.</P>

<H3><CODE><A NAME="hash_map::key_comp">hash_map::key_comp</A></CODE></H3>

<PRE>key_compare <B>key_comp</B>() const;</PRE>

<P>The member function returns the stored
<A HREF="#hash traits">hash traits</A> object that
determines the order of elements in the controlled sequence.
In particular, the stored object defines the member function:</P>

<PRE>bool operator()(const Key&amp; left, const Key&amp; right);</PRE>

<P>which returns true if <CODE>left</CODE> strictly
precedes <CODE>right</CODE> in the sort order.</P>

<H3><CODE><A NAME="hash_map::key_compare">hash_map::key_compare</A></CODE></H3>

<PRE>typedef Tr <B>key_compare</B>;</PRE>

<P>The type describes a traits object that behaves much like an object of class
<CODE><A HREF="#hash_compare">hash_compare</A>&lt;Key, Pr&gt;</CODE>.
In particular, it can compare two
sort keys to determine the relative order of two
elements in the controlled sequence.</P>

<H3><CODE><A NAME="hash_map::key_type">hash_map::key_type</A></CODE></H3>

<PRE>typedef Key <B>key_type</B>;</PRE>