📄 hash_map.html
字号:
<HTML>
<HEAD>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<META NAME="Author" CONTENT="Zafir Anjum">
<TITLE>MFC Programmer's SourceBook : STL Programmer's Guide</TITLE>
<META name="description"
content="A freely available implementation
of the C++ Standard Template Library, including
hypertext documentation.">
<META name="keywords"
content="generic programming, STL, standard template library">
</HEAD>
<SCRIPT LANGUAGE="JavaScript"><!--
var adcategory = "cpp";
// -->
</SCRIPT>
<body background="../../fancyhome/back.gif" bgcolor="#FFFFFF" >
<SCRIPT LANGUAGE="JavaScript"><!--
var nfrm = location.href.indexOf("_nfrm_");
var validframes = (top.frames.length > 0 && top.frames['ad'] && top.frames['logo'] );
var random = Math.random();
if( !validframes && nfrm == -1 )
{
var dclkPage = "www.codeguru.com/";
if( self.adcategory )
dclkPage += adcategory;
else
dclkPage += "mfc";
document.write('<nolayer><center>');
document.write('<iframe src="http://ad.doubleclick.net/adi/' + dclkPage + ';ord='
+ random + '" width=470 height=62 marginwidth=0 marginheight=0 hspace=0 vspace=0 '
+ 'frameborder=0 scrolling=no bordercolor="#000000">');
document.write('<a href="http://ad.doubleclick.net/jump/' + dclkPage + ';ord='
+ random + '">');
document.write('<img src="http://ad.doubleclick.net/ad/' + dclkPage + ';ord='
+ random + '" height=60 width=468>' + '</a>');
document.write('</iframe>');
document.write('</center></nolayer>');
document.write('<layer src="http://ad.doubleclick.net/adl/' + dclkPage +
';ord=' + random + '"></layer>');
document.write('<ilayer visibility=hide width=468 height=83></ilayer>');
}
// top.location = "/show.cgi?" + adcategory + "=" + location.pathname;
// -->
</SCRIPT>
<noscript>
<p align="center">
<a href="http://ad.doubleclick.net/jump/www.codeguru.com/cpp;ord=NupaT9FCY34AAHeYcHE">
<img src="http://ad.doubleclick.net/ad/www.codeguru.com/cpp;ord=NupaT9FCY34AAHeYcHE"></a>
</p>
</noscript>
<BR Clear>
<H1>hash_map<Key, Data, HashFcn, EqualKey, Alloc></H1>
<Table CellPadding=0 CellSpacing=0 width=100%>
<TR>
<TD Align=left><Img src = "containers.gif" Alt="" WIDTH = "194" HEIGHT = "38" ></TD>
<TD Align=right><Img src = "type.gif" Alt="" WIDTH = "194" HEIGHT = "39" ></TD>
</TR>
<TR>
<TD Align=left VAlign=top><b>Category</b>: containers</TD>
<TD Align=right VAlign=top><b>Component type</b>: type</TD>
</TR>
</Table>
<h3>Description</h3>
<tt>Hash_map</tt> is a
<A href="HashedAssociativeContainer.html">Hashed Associative Container</A>
that associates objects of type <tt>Key</tt> with
objects of type <tt>Data</tt>. <tt>Hash_map</tt> is a
<A href="PairAssociativeContainer.html">Pair Associative Container</A>,
meaning that its value type is
<tt><A href="pair.html">pair</A><const Key, Data></tt>. It is also a
<A href="UniqueAssociativeContainer.html">Unique Associative Container</A>,
meaning that no two elements have keys that compare
equal using <tt>EqualKey</tt>.
<P>
Looking up an element in a <tt>hash_map</tt> by its key is efficient,
so <tt>hash_map</tt> is useful for "dictionaries" where the
order of elements is irrelevant. If it is important for the elements
to be in a particular order, however, then
<tt><A href="Map.html">map</A></tt> is more appropriate.
<h3>Example</h3>
<pre>
struct eqstr
{
bool operator()(const char* s1, const char* s2) const
{
return strcmp(s1, s2) == 0;
}
};
int main()
{
hash_map<const char*, int, hash<const char*>, eqstr> months;
months["january"] = 31;
months["february"] = 28;
months["march"] = 31;
months["april"] = 30;
months["may"] = 31;
months["june"] = 30;
months["july"] = 31;
months["august"] = 31;
months["september"] = 30;
months["october"] = 31;
months["november"] = 30;
months["december"] = 31;
cout << "september -> " << months["september"] << endl;
cout << "april -> " << months["april"] << endl;
cout << "june -> " << months["june"] << endl;
cout << "november -> " << months["november"] << endl;
}
</pre>
<h3>Definition</h3>
<tt>Hash_map</tt> is declared in <A href="hash_map.h">hash_map.h</A>.
The implementation is in <A href="hash_map.h">hash_map.h</A> and
<A href="hashtable.h">hashtable.h</A>.
<h3>Template parameters</h3>
<Table border>
<TR>
<TH>
Parameter
</TH>
<TH>
Description
</TH>
<TH>
Default
</TH>
</TR>
<TR>
<TD VAlign=top>
<tt>Key</tt>
</TD>
<TD VAlign=top>
The hash_map's key type. This is also defined as <tt>hash_map::key_type</tt>.
</TD>
<TD VAlign=top>
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>Data</tt>
</TD>
<TD VAlign=top>
The hash_map's data type. This is also defined as <tt>hash_map::data_type</tt>.
</TD>
<TD VAlign=top>
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>HashFcn</tt>
</TD>
<TD VAlign=top>
The <A href="HashFunction.html">hash function</A> used by the hash_map. This is also defined
as <tt>hash_map::hasher</tt>.
</TD>
<TD VAlign=top>
<tt><A href="hash.html">hash</A><Key></tt>
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>EqualKey</tt>
</TD>
<TD VAlign=top>
The hash_map key equality function: a <A href="BinaryPredicate.html">binary predicate</A> that
determines whether two keys are equal. This is also defined as
<tt>hash_map::key_equal</tt>.
</TD>
<TD VAlign=top>
<tt><A href="equal_to.html">equal_to</A><Key></tt>
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>Alloc</tt>
</TD>
<TD VAlign=top>
The <tt>hash_map</tt>'s allocator, used for all internal memory management.
</TD>
<TD VAlign=top>
<tt><A href="Allocators.html">alloc</A></tt>
</TD>
</tr>
</table>
<h3>Model of</h3>
<A href="UniqueHashedAssociativeContainer.html">Unique Hashed Associative Container</A>,
<A href="PairAssociativeContainer.html">Pair Associative Container</A>
<h3>Type requirements</h3>
<UL>
<LI>
<tt>Key</tt> is <A href="Assignable.html">Assignable</A>.
<LI>
<tt>EqualKey</tt> is a <A href="BinaryPredicate.html">Binary Predicate</A> whose argument type
is <tt>Key</tt>.
<LI>
<tt>EqualKey</tt> is an equivalence relation.
<LI>
<tt>Alloc</tt> is an <A href="Allocators.html">Allocator</A>.
</UL>
<h3>Public base classes</h3>
None.
<h3>Members</h3>
<Table border>
<TR>
<TH>
Member
</TH>
<TH>
Where defined
</TH>
<TH>
Description
</TH>
</TR>
<TR>
<TD VAlign=top>
<tt>key_type</tt>
</TD>
<TD VAlign=top>
<A href="AssociativeContainer.html">Associative Container</A>
</TD>
<TD VAlign=top>
The <tt>hash_map</tt>'s key type, <tt>Key</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>data_type</tt>
</TD>
<TD VAlign=top>
<A href="PairAssociativeContainer.html">Pair Associative Container</A>
</TD>
<TD VAlign=top>
The type of object associated with the keys.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>value_type</tt>
</TD>
<TD VAlign=top>
<A href="PairAssociativeContainer.html">Pair Associative Container</A>
</TD>
<TD VAlign=top>
The type of object, <tt>pair<const key_type, data_type></tt>, stored in the hash_map.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>hasher</tt>
</TD>
<TD VAlign=top>
<A href="HashedAssociativeContainer.html">Hashed Associative Container</A>
</TD>
<TD VAlign=top>
The <tt>hash_map</tt>'s <A href="HashFunction.html">hash function</A>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>key_equal</tt>
</TD>
<TD VAlign=top>
<A href="HashedAssociativeContainer.html">Hashed Associative Container</A>
</TD>
<TD VAlign=top>
<A href="functors.html">Function object</A> that compares keys for equality.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>pointer</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Pointer to <tt>T</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>reference</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Reference to <tt>T</tt>
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>const_reference</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Const reference to <tt>T</tt>
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>size_type</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
An unsigned integral type.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>difference_type</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
A signed integral type.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>iterator</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Iterator used to iterate through a <tt>hash_map</tt>. <A href="#1">[1]</A>
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>const_iterator</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Const iterator used to iterate through a <tt>hash_map</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>iterator begin()</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Returns an <tt>iterator</tt> pointing to the beginning of the <tt>hash_map</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>iterator end()</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Returns an <tt>iterator</tt> pointing to the end of the <tt>hash_map</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>const_iterator begin() const</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Returns an <tt>const_iterator</tt> pointing to the beginning of the <tt>hash_map</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>const_iterator end() const</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Returns an <tt>const_iterator</tt> pointing to the end of the <tt>hash_map</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>size_type size() const</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Returns the size of the <tt>hash_map</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>size_type max_size() const</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
Returns the largest possible size of the <tt>hash_map</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>bool empty() const</tt>
</TD>
<TD VAlign=top>
<A href="Container.html">Container</A>
</TD>
<TD VAlign=top>
<tt>true</tt> if the <tt>hash_map</tt>'s size is <tt>0</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>size_type bucket_count() const</tt>
</TD>
<TD VAlign=top>
<A href="HashedAssociativeContainer.html">Hashed Associative Container</A>
</TD>
<TD VAlign=top>
Returns the number of buckets used by the <tt>hash_map</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>void resize(size_type n)</tt>
</TD>
<TD VAlign=top>
<A href="HashedAssociativeContainer.html">Hashed Associative Container</A>
</TD>
<TD VAlign=top>
Increases the bucket count to at least <tt>n</tt>.
</TD>
</TR>
<TR>
<TD VAlign=top>
<tt>hasher hash_funct() const</tt>
</TD>
<TD VAlign=top>
<A href="HashedAssociativeContainer.html">Hashed Associative Container</A>
</TD>
<TD VAlign=top>
Returns the <tt>hasher</tt> object used by the <tt>hash_map</tt>.
</TD>
</TR>
⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -