[2162] | 1 | <HTML>
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| 2 | <!-- The API of this class and the documentation -- but not the
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| 3 | implementation! -- are based on that for SGI's hash_set class:
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| 4 | -->
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| 5 | <!--
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| 6 | -- Copyright (c) 1996-1999
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| 7 | -- Silicon Graphics Computer Systems, Inc.
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| 8 | --
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| 9 | -- Permission to use, copy, modify, distribute and sell this software
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| 10 | -- and its documentation for any purpose is hereby granted without fee,
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| 11 | -- provided that the above copyright notice appears in all copies and
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| 12 | -- that both that copyright notice and this permission notice appear
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| 13 | -- in supporting documentation. Silicon Graphics makes no
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| 14 | -- representations about the suitability of this software for any
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| 15 | -- purpose. It is provided "as is" without express or implied warranty.
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| 16 | --
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| 17 | -- Copyright (c) 1994
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| 18 | -- Hewlett-Packard Company
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| 19 | --
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| 20 | -- Permission to use, copy, modify, distribute and sell this software
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| 21 | -- and its documentation for any purpose is hereby granted without fee,
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| 22 | -- provided that the above copyright notice appears in all copies and
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| 23 | -- that both that copyright notice and this permission notice appear
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| 24 | -- in supporting documentation. Hewlett-Packard Company makes no
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| 25 | -- representations about the suitability of this software for any
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| 26 | -- purpose. It is provided "as is" without express or implied warranty.
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| 27 | --
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| 28 | -->
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| 29 |
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| 30 | <HEAD>
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| 31 | <Title>dense_hash_set<Key, HashFcn, EqualKey, Alloc></Title>
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| 32 | </HEAD>
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| 33 |
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| 34 | <BODY>
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| 35 |
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| 36 | <p><i>[Note: this document is formatted similarly to the SGI STL
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| 37 | implementation documentation pages, and refers to concepts and classes
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| 38 | defined there. However, neither this document nor the code it
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| 39 | describes is associated with SGI, nor is it necessary to have SGI's
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| 40 | STL implementation installed in order to use this class.]</i></p>
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| 41 |
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| 42 |
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| 43 | <H1>dense_hash_set<Key, HashFcn, EqualKey, Alloc></H1>
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| 44 |
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| 45 | <p><tt>dense_hash_set</tt> is a <A
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| 46 | href="http://www.sgi.com/tech/stl/HashedAssociativeContainer.html">Hashed
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| 47 | Associative Container</A> that stores objects of type <tt>Key</tt>.
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| 48 | <tt>dense_hash_set</tt> is a <A
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| 49 | href="http://www.sgi.com/tech/stl/SimpleAssociativeContainer.html">Simple
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| 50 | Associative Container</A>, meaning that its value type, as well as its
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| 51 | key type, is <tt>key</tt> It is also a
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| 52 | <A
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| 53 | href="http://www.sgi.com/tech/stl/UniqueAssociativeContainer.html">Unique
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| 54 | Associative Container</A>, meaning that no two elements have keys that
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| 55 | compare equal using <tt>EqualKey</tt>.</p>
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| 56 |
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| 57 | <p>Looking up an element in a <tt>dense_hash_set</tt> by its key is
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| 58 | efficient, so <tt>dense_hash_set</tt> is useful for "dictionaries"
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| 59 | where the order of elements is irrelevant. If it is important for the
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| 60 | elements to be in a particular order, however, then <tt><A
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| 61 | href="http://www.sgi.com/tech/stl/Map.html">map</A></tt> is more appropriate.</p>
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| 62 |
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| 63 | <p><tt>dense_hash_set</tt> is distinguished from other hash-set
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| 64 | implementations by its speed and by the ability to save
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| 65 | and restore contents to disk. On the other hand, this hash-set
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| 66 | implementation can use significantly more space than other hash-set
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| 67 | implementations, and it also has requirements -- for instance, for a
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| 68 | distinguished "empty key" -- that may not be easy for all
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| 69 | applications to satisfy.</p>
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| 70 |
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| 71 | <p>This class is appropriate for applications that need speedy access
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| 72 | to relatively small "dictionaries" stored in memory, and for
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| 73 | applications that need these dictionaries to be persistent. <A
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| 74 | HREF="#io">[implementation note]</A>)</p>
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| 75 |
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| 76 |
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| 77 | <h3>Example</h3>
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| 78 |
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| 79 | <pre>
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| 80 | #include <google/dense_hash_set>
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| 81 |
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| 82 | using std::dense_hash_set; // namespace where class lives by default
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| 83 |
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| 84 | struct eqstr
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| 85 | {
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| 86 | bool operator()(const char* s1, const char* s2) const
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| 87 | {
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| 88 | return strcmp(s1, s2) == 0;
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| 89 | }
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| 90 | };
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| 91 |
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| 92 | void lookup(const hash_set<const char*, hash<const char*>, eqstr>& Set,
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| 93 | const char* word)
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| 94 | {
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| 95 | dense_hash_set<const char*, hash<const char*>, eqstr>::const_iterator it
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| 96 | = Set.find(word);
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| 97 | cout << word << ": "
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| 98 | << (it != Set.end() ? "present" : "not present")
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| 99 | << endl;
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| 100 | }
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| 101 |
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| 102 | int main()
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| 103 | {
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| 104 | dense_hash_set<const char*, hash<const char*>, eqstr> Set;
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| 105 | Set.set_empty_key(NULL);
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| 106 | Set.insert("kiwi");
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| 107 | Set.insert("plum");
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| 108 | Set.insert("apple");
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| 109 | Set.insert("mango");
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| 110 | Set.insert("apricot");
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| 111 | Set.insert("banana");
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| 112 |
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| 113 | lookup(Set, "mango");
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| 114 | lookup(Set, "apple");
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| 115 | lookup(Set, "durian");
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| 116 | }
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| 117 | </pre>
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| 118 |
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| 119 |
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| 120 | <h3>Definition</h3>
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| 121 |
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| 122 | Defined in the header <A
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| 123 | href="dense_hash_set.h">dense_hash_set.h</A>. This class is not
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| 124 | part of the C++ standard.
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| 125 |
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| 126 |
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| 127 | <h3>Template parameters</h3>
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| 128 |
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| 129 | <table border>
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| 130 | <TR><TH>Parameter</TH><TH>Description</TH><TH>Default</TH></TR>
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| 131 |
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| 132 | <TR>
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| 133 | <TD VAlign=top>
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| 134 | <tt>Key</tt>
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| 135 | </TD>
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| 136 | <TD VAlign=top>
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| 137 | The hash_set's key and value type. This is also defined as
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| 138 | <tt>dense_hash_set::key_type</tt> and
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| 139 | <tt>dense_hash_set::value_type</tt>.
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| 140 | </TD>
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| 141 | <TD VAlign=top>
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| 142 |
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| 143 | </TD>
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| 144 | </TR>
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| 145 |
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| 146 | <TR>
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| 147 | <TD VAlign=top>
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| 148 | <tt>Data</tt>
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| 149 | </TD>
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| 150 | <TD VAlign=top>
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| 151 | The hash_set's data type. This is also defined as
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| 152 | <tt>dense_hash_set::data_type</tt>.
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| 153 | </TD>
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| 154 | <TD VAlign=top>
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| 155 |
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| 156 | </TD>
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| 157 | </TR>
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| 158 |
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| 159 | <TR>
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| 160 | <TD VAlign=top>
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| 161 | <tt>HashFcn</tt>
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| 162 | </TD>
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| 163 | <TD VAlign=top>
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| 164 | The <A href="http://www.sgi.com/tech/stl/HashFunction.html">hash function</A> used by the
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| 165 | hash_set. This is also defined as <tt>dense_hash_set::hasher</tt>.
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| 166 | <br><b>Note:</b> Hashtable performance depends heavliy on the choice of
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| 167 | hash function. See <A HREF="performance.html#hashfn">the performance
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| 168 | page</A> for more information.
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| 169 | </TD>
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| 170 | <TD VAlign=top>
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| 171 | <tt><A href="http://www.sgi.com/tech/stl/hash.html">hash</A><Key></tt>
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| 172 | </TD>
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| 173 | </TR>
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| 174 |
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| 175 | <TR>
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| 176 | <TD VAlign=top>
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| 177 | <tt>EqualKey</tt>
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| 178 | </TD>
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| 179 | <TD VAlign=top>
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| 180 | The hash_set key equality function: a <A
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| 181 | href="http://www.sgi.com/tech/stl/BinaryPredicate.html">binary predicate</A> that determines
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| 182 | whether two keys are equal. This is also defined as
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| 183 | <tt>dense_hash_set::key_equal</tt>.
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| 184 | </TD>
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| 185 | <TD VAlign=top>
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| 186 | <tt><A href="http://www.sgi.com/tech/stl/equal_to.html">equal_to</A><Key></tt>
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| 187 | </TD>
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| 188 | </TR>
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| 189 |
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| 190 | <TR>
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| 191 | <TD VAlign=top>
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| 192 | <tt>Alloc</tt>
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| 193 | </TD>
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| 194 | <TD VAlign=top>
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| 195 | <b>Ignored</b>; this is included only for API-compatibility
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| 196 | with SGI's STL implementation.
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| 197 | </TD>
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| 198 | <TD VAlign=top>
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| 199 | <tt><A href="http://www.sgi.com/tech/stl/Allocators.html">alloc</A></tt>
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| 200 | </TD>
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| 201 | </TR>
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| 202 |
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| 203 | </table>
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| 204 |
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| 205 |
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| 206 | <h3>Model of</h3>
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| 207 |
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| 208 | <A href="http://www.sgi.com/tech/stl/UniqueHashedAssociativeContainer.html">Unique Hashed Associative Container</A>,
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| 209 | <A href="http://www.sgi.com/tech/stl/SimpleAssociativeContainer.html">Simple Associative Container</A>
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| 210 |
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| 211 |
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| 212 | <h3>Type requirements</h3>
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| 213 |
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| 214 | <UL>
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| 215 | <LI>
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| 216 | <tt>Key</tt> is Assignable.
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| 217 | <LI>
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| 218 | <tt>EqualKey</tt> is a Binary Predicate whose argument type is Key.
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| 219 | <LI>
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| 220 | <tt>EqualKey</tt> is an equivalence relation.
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| 221 | <LI>
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| 222 | <tt>Alloc</tt> is an Allocator.
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| 223 | </UL>
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| 224 |
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| 225 |
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| 226 | <h3>Public base classes</h3>
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| 227 |
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| 228 | None.
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| 229 |
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| 230 |
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| 231 | <h3>Members</h3>
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| 232 |
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| 233 | <table border>
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| 234 | <TR><TH>Member</TH><TH>Where defined</TH><TH>Description</TH></TR>
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| 235 |
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| 236 | <TR>
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| 237 | <TD VAlign=top>
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| 238 | <tt>value_type</tt> <A href="#5">[7]</A>
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| 239 | </TD>
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| 240 | <TD VAlign=top>
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| 241 | <A
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| 242 | href="http://www.sgi.com/tech/stl/Container.html">Container</A>
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| 243 | </TD>
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| 244 | <TD VAlign=top>
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| 245 | The type of object, <tt>T</tt>, stored in the hash_set.
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| 246 | </TD>
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| 247 | </TR>
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| 248 |
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| 249 | <TR>
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| 250 | <TD VAlign=top>
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| 251 | <tt>key_type</tt>
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| 252 | </TD>
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| 253 | <TD VAlign=top>
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| 254 | <A
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| 255 | href="http://www.sgi.com/tech/stl/AssociativeContainer.html">Associative
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| 256 | Container</A>
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| 257 | </TD>
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| 258 | <TD VAlign=top>
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| 259 | The key type associated with <tt>value_type</tt>.
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| 260 | </TD>
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| 261 | </TR>
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| 262 |
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| 263 | <TR>
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| 264 | <TD VAlign=top>
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| 265 | <tt>hasher</tt>
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| 266 | </TD>
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| 267 | <TD VAlign=top>
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| 268 | <A
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| 269 | href="http://www.sgi.com/tech/stl/HashedAssociativeContainer.html">Hashed
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| 270 | Associative Container</A>
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| 271 | </TD>
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| 272 | <TD VAlign=top>
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| 273 | The <tt>dense_hash_set</tt>'s <A
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| 274 | href="http://www.sgi.com/tech/stl/HashFunction.html">hash
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| 275 | function</A>.
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| 276 | </TD>
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| 277 | </TR>
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| 278 |
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| 279 | <TR>
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| 280 | <TD VAlign=top>
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| 281 | <tt>key_equal</tt>
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| 282 | </TD>
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| 283 | <TD VAlign=top>
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| 284 | <A
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| 285 | href="http://www.sgi.com/tech/stl/HashedAssociativeContainer.html">Hashed
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| 286 | Associative Container</A>
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| 287 | </TD>
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| 288 | <TD VAlign=top>
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| 289 | <A href="http://www.sgi.com/tech/stl/functors.html">Function
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| 290 | object</A> that compares keys for equality.
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| 291 | </TD>
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| 292 | </TR>
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| 293 |
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| 294 | <TR>
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| 295 | <TD VAlign=top>
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| 296 | <tt>pointer</tt>
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| 297 | </TD>
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| 298 | <TD VAlign=top>
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| 299 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
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| 300 | </TD>
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| 301 | <TD VAlign=top>
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| 302 | Pointer to <tt>T</tt>.
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| 303 | </TD>
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| 304 | </TR>
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| 305 |
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| 306 | <TR>
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| 307 | <TD VAlign=top>
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| 308 | <tt>reference</tt>
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| 309 | </TD>
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| 310 | <TD VAlign=top>
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| 311 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
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| 312 | </TD>
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| 313 | <TD VAlign=top>
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| 314 | Reference to <tt>T</tt>
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| 315 | </TD>
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| 316 | </TR>
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| 317 |
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| 318 | <TR>
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| 319 | <TD VAlign=top>
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| 320 | <tt>const_reference</tt>
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| 321 | </TD>
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| 322 | <TD VAlign=top>
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| 323 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
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| 324 | </TD>
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| 325 | <TD VAlign=top>
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| 326 | Const reference to <tt>T</tt>
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| 327 | </TD>
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| 328 | </TR>
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| 329 |
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| 330 | <TR>
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| 331 | <TD VAlign=top>
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| 332 | <tt>size_type</tt>
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| 333 | </TD>
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| 334 | <TD VAlign=top>
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| 335 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
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| 336 | </TD>
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| 337 | <TD VAlign=top>
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| 338 | An unsigned integral type.
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| 339 | </TD>
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| 340 | </TR>
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| 341 |
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| 342 | <TR>
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| 343 | <TD VAlign=top>
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| 344 | <tt>difference_type</tt>
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| 345 | </TD>
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| 346 | <TD VAlign=top>
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| 347 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
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| 348 | </TD>
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| 349 | <TD VAlign=top>
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| 350 | A signed integral type.
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| 351 | </TD>
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| 352 | </TR>
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| 353 |
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| 354 | <TR>
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| 355 | <TD VAlign=top>
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| 356 | <tt>iterator</tt>
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| 357 | </TD>
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| 358 | <TD VAlign=top>
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| 359 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
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| 360 | </TD>
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| 361 | <TD VAlign=top>
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| 362 | Iterator used to iterate through a <tt>dense_hash_set</tt>.
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| 363 | </TD>
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| 364 | </TR>
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| 365 |
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| 366 | <TR>
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| 367 | <TD VAlign=top>
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| 368 | <tt>const_iterator</tt>
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| 369 | </TD>
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| 370 | <TD VAlign=top>
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| 371 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
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| 372 | </TD>
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| 373 | <TD VAlign=top>
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| 374 | Const iterator used to iterate through a <tt>dense_hash_set</tt>.
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| 375 | (<tt>iterator</tt> and <tt>const_iterator</tt> are the same type.)
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| 376 | </TD>
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| 377 | </TR>
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| 378 |
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| 379 | <TR>
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| 380 | <TD VAlign=top>
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| 381 | <tt>iterator begin() const</tt>
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| 382 | </TD>
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| 383 | <TD VAlign=top>
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| 384 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
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| 385 | </TD>
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| 386 | <TD VAlign=top>
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| 387 | Returns an <tt>iterator</tt> pointing to the beginning of the
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| 388 | <tt>dense_hash_set</tt>.
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| 389 | </TD>
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| 390 | </TR>
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| 391 |
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| 392 | <TR>
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| 393 | <TD VAlign=top>
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| 394 | <tt>iterator end() const</tt>
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| 395 | </TD>
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| 396 | <TD VAlign=top>
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| 397 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
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| 398 | </TD>
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| 399 | <TD VAlign=top>
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| 400 | Returns an <tt>iterator</tt> pointing to the end of the
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| 401 | <tt>dense_hash_set</tt>.
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| 402 | </TD>
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| 403 | </TR>
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| 404 |
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| 405 | <TR>
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| 406 | <TD VAlign=top>
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| 407 | <tt>size_type size() const</tt>
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| 408 | </TD>
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| 409 | <TD VAlign=top>
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| 410 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
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| 411 | </TD>
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| 412 | <TD VAlign=top>
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| 413 | Returns the size of the <tt>dense_hash_set</tt>.
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| 414 | </TD>
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| 415 | </TR>
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| 416 |
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| 417 | <TR>
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| 418 | <TD VAlign=top>
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| 419 | <tt>size_type max_size() const</tt>
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| 420 | </TD>
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| 421 | <TD VAlign=top>
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| 422 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
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| 423 | </TD>
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| 424 | <TD VAlign=top>
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| 425 | Returns the largest possible size of the <tt>dense_hash_set</tt>.
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| 426 | </TD>
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| 427 | </TR>
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| 428 |
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| 429 | <TR>
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| 430 | <TD VAlign=top>
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| 431 | <tt>bool empty() const</tt>
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| 432 | </TD>
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| 433 | <TD VAlign=top>
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| 434 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
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| 435 | </TD>
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| 436 | <TD VAlign=top>
|
---|
| 437 | <tt>true</tt> if the <tt>dense_hash_set</tt>'s size is <tt>0</tt>.
|
---|
| 438 | </TD>
|
---|
| 439 | </TR>
|
---|
| 440 |
|
---|
| 441 | <TR>
|
---|
| 442 | <TD VAlign=top>
|
---|
| 443 | <tt>size_type bucket_count() const</tt>
|
---|
| 444 | </TD>
|
---|
| 445 | <TD VAlign=top>
|
---|
| 446 | <A
|
---|
| 447 | href="http://www.sgi.com/tech/stl/HashedAssociativeContainer.html">Hashed
|
---|
| 448 | Associative Container</A>
|
---|
| 449 | </TD>
|
---|
| 450 | <TD VAlign=top>
|
---|
| 451 | Returns the number of buckets used by the <tt>dense_hash_set</tt>.
|
---|
| 452 | </TD>
|
---|
| 453 | </TR>
|
---|
| 454 |
|
---|
| 455 | <TR>
|
---|
| 456 | <TD VAlign=top>
|
---|
| 457 | <tt>size_type max_bucket_count() const</tt>
|
---|
| 458 | </TD>
|
---|
| 459 | <TD VAlign=top>
|
---|
| 460 | <A
|
---|
| 461 | href="http://www.sgi.com/tech/stl/HashedAssociativeContainer.html">Hashed
|
---|
| 462 | Associative Container</A>
|
---|
| 463 | </TD>
|
---|
| 464 | <TD VAlign=top>
|
---|
| 465 | Returns the largest possible number of buckets used by the <tt>dense_hash_set</tt>.
|
---|
| 466 | </TD>
|
---|
| 467 | </TR>
|
---|
| 468 |
|
---|
| 469 | <TR>
|
---|
| 470 | <TD VAlign=top>
|
---|
| 471 | <tt>void resize(size_type n)</tt>
|
---|
| 472 | </TD>
|
---|
| 473 | <TD VAlign=top>
|
---|
| 474 | <A
|
---|
| 475 | href="http://www.sgi.com/tech/stl/HashedAssociativeContainer.html">Hashed
|
---|
| 476 | Associative Container</A>
|
---|
| 477 | </TD>
|
---|
| 478 | <TD VAlign=top>
|
---|
| 479 | Increases the bucket count to at least <tt>n</tt>.
|
---|
| 480 | <A href="#2">[4]</A>
|
---|
| 481 | </TD>
|
---|
| 482 | </TR>
|
---|
| 483 |
|
---|
| 484 | <TR>
|
---|
| 485 | <TD VAlign=top>
|
---|
| 486 | <tt>hasher hash_funct() const</tt>
|
---|
| 487 | </TD>
|
---|
| 488 | <TD VAlign=top>
|
---|
| 489 | <A
|
---|
| 490 | href="http://www.sgi.com/tech/stl/HashedAssociativeContainer.html">Hashed
|
---|
| 491 | Associative Container</A>
|
---|
| 492 | </TD>
|
---|
| 493 | <TD VAlign=top>
|
---|
| 494 | Returns the <tt>hasher</tt> object used by the <tt>dense_hash_set</tt>.
|
---|
| 495 | </TD>
|
---|
| 496 | </TR>
|
---|
| 497 |
|
---|
| 498 | <TR>
|
---|
| 499 | <TD VAlign=top>
|
---|
| 500 | <tt>key_equal key_eq() const</tt>
|
---|
| 501 | </TD>
|
---|
| 502 | <TD VAlign=top>
|
---|
| 503 | <A
|
---|
| 504 | href="http://www.sgi.com/tech/stl/HashedAssociativeContainer.html">Hashed
|
---|
| 505 | Associative Container</A>
|
---|
| 506 | </TD>
|
---|
| 507 | <TD VAlign=top>
|
---|
| 508 | Returns the <tt>key_equal</tt> object used by the
|
---|
| 509 | <tt>dense_hash_set</tt>.
|
---|
| 510 | </TD>
|
---|
| 511 | </TR>
|
---|
| 512 |
|
---|
| 513 | <TR>
|
---|
| 514 | <TD VAlign=top>
|
---|
| 515 | <tt>dense_hash_set()</tt>
|
---|
| 516 | </TD>
|
---|
| 517 | <TD VAlign=top>
|
---|
| 518 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
|
---|
| 519 | </TD>
|
---|
| 520 | <TD VAlign=top>
|
---|
| 521 | Creates an empty <tt>dense_hash_set</tt>.
|
---|
| 522 | </TD>
|
---|
| 523 | </TR>
|
---|
| 524 |
|
---|
| 525 | <TR>
|
---|
| 526 | <TD VAlign=top>
|
---|
| 527 | <tt>dense_hash_set(size_type n)</tt>
|
---|
| 528 | </TD>
|
---|
| 529 | <TD VAlign=top>
|
---|
| 530 | <A
|
---|
| 531 | href="http://www.sgi.com/tech/stl/HashedAssociativeContainer.html">Hashed
|
---|
| 532 | Associative Container</A>
|
---|
| 533 | </TD>
|
---|
| 534 | <TD VAlign=top>
|
---|
| 535 | Creates an empty <tt>dense_hash_set</tt> that's optimized for holding
|
---|
| 536 | up to <tt>n</tt> items.
|
---|
| 537 | <A href="#3">[5]</A>
|
---|
| 538 | </TD>
|
---|
| 539 | </TR>
|
---|
| 540 |
|
---|
| 541 | <TR>
|
---|
| 542 | <TD VAlign=top>
|
---|
| 543 | <tt>dense_hash_set(size_type n, const hasher& h)</tt>
|
---|
| 544 | </TD>
|
---|
| 545 | <TD VAlign=top>
|
---|
| 546 | <A
|
---|
| 547 | href="http://www.sgi.com/tech/stl/HashedAssociativeContainer.html">Hashed
|
---|
| 548 | Associative Container</A>
|
---|
| 549 | </TD>
|
---|
| 550 | <TD VAlign=top>
|
---|
| 551 | Creates an empty <tt>dense_hash_set</tt> that's optimized for up
|
---|
| 552 | to <tt>n</tt> items, using <tt>h</tt> as the hash function.
|
---|
| 553 | </TD>
|
---|
| 554 | </TR>
|
---|
| 555 |
|
---|
| 556 | <TR>
|
---|
| 557 | <TD VAlign=top>
|
---|
| 558 | <tt>dense_hash_set(size_type n, const hasher& h, const
|
---|
| 559 | key_equal& k)</tt>
|
---|
| 560 | </TD>
|
---|
| 561 | <TD VAlign=top>
|
---|
| 562 | <A
|
---|
| 563 | href="http://www.sgi.com/tech/stl/HashedAssociativeContainer.html">Hashed
|
---|
| 564 | Associative Container</A>
|
---|
| 565 | </TD>
|
---|
| 566 | <TD VAlign=top>
|
---|
| 567 | Creates an empty <tt>dense_hash_set</tt> that's optimized for up
|
---|
| 568 | to <tt>n</tt> items, using <tt>h</tt> as the hash function and
|
---|
| 569 | <tt>k</tt> as the key equal function.
|
---|
| 570 | </TD>
|
---|
| 571 | </TR>
|
---|
| 572 |
|
---|
| 573 | <TR>
|
---|
| 574 | <TD VAlign=top>
|
---|
| 575 | <pre>template <class <A
|
---|
| 576 | href="http://www.sgi.com/tech/stl/InputIterator.html">InputIterator</A>>
|
---|
| 577 | dense_hash_set(InputIterator f, InputIterator l) </pre>
|
---|
| 578 | <A href="#1">[2]</A>
|
---|
| 579 | </TD>
|
---|
| 580 | <TD VAlign=top>
|
---|
| 581 | <A
|
---|
| 582 | href="http://www.sgi.com/tech/stl/UniqueHashedAssociativeContainer.html">Unique
|
---|
| 583 | Hashed Associative Container</A>
|
---|
| 584 | </TD>
|
---|
| 585 | <TD VAlign=top>
|
---|
| 586 | Creates a dense_hash_set with a copy of a range.
|
---|
| 587 | </TD>
|
---|
| 588 | </TR>
|
---|
| 589 |
|
---|
| 590 | <TR>
|
---|
| 591 | <TD VAlign=top>
|
---|
| 592 | <pre>template <class <A
|
---|
| 593 | href="http://www.sgi.com/tech/stl/InputIterator.html">InputIterator</A>>
|
---|
| 594 | dense_hash_set(InputIterator f, InputIterator l, size_type n) </pre>
|
---|
| 595 | <A href="#1">[2]</A>
|
---|
| 596 | </TD>
|
---|
| 597 | <TD VAlign=top>
|
---|
| 598 | <A
|
---|
| 599 | href="http://www.sgi.com/tech/stl/UniqueHashedAssociativeContainer.html">Unique
|
---|
| 600 | Hashed Associative Container</A>
|
---|
| 601 | </TD>
|
---|
| 602 | <TD VAlign=top>
|
---|
| 603 | Creates a hash_set with a copy of a range that's optimized to
|
---|
| 604 | hold up to <tt>n</tt> items.
|
---|
| 605 | </TD>
|
---|
| 606 | </TR>
|
---|
| 607 |
|
---|
| 608 | <TR>
|
---|
| 609 | <TD VAlign=top>
|
---|
| 610 | <pre>template <class <A
|
---|
| 611 | href="http://www.sgi.com/tech/stl/InputIterator.html">InputIterator</A>>
|
---|
| 612 | dense_hash_set(InputIterator f, InputIterator l, size_type n, const
|
---|
| 613 | hasher& h) </pre> <A href="#1">[2]</A>
|
---|
| 614 | </TD>
|
---|
| 615 | <TD VAlign=top>
|
---|
| 616 | <A
|
---|
| 617 | href="http://www.sgi.com/tech/stl/UniqueHashedAssociativeContainer.html">Unique
|
---|
| 618 | Hashed Associative Container</A>
|
---|
| 619 | </TD>
|
---|
| 620 | <TD VAlign=top>
|
---|
| 621 | Creates a hash_set with a copy of a range that's optimized to hold
|
---|
| 622 | up to <tt>n</tt> items, using <tt>h</tt> as the hash function.
|
---|
| 623 | </TD>
|
---|
| 624 | </TR>
|
---|
| 625 |
|
---|
| 626 | <TR>
|
---|
| 627 | <TD VAlign=top>
|
---|
| 628 | <pre>template <class <A
|
---|
| 629 | href="http://www.sgi.com/tech/stl/InputIterator.html">InputIterator</A>>
|
---|
| 630 | dense_hash_set(InputIterator f, InputIterator l, size_type n, const
|
---|
| 631 | hasher& h, const key_equal& k) </pre> <A href="#1">[2]</A>
|
---|
| 632 | </TD>
|
---|
| 633 | <TD VAlign=top>
|
---|
| 634 | <A
|
---|
| 635 | href="http://www.sgi.com/tech/stl/UniqueHashedAssociativeContainer.html">Unique
|
---|
| 636 | Hashed Associative Container</A>
|
---|
| 637 | </TD>
|
---|
| 638 | <TD VAlign=top>
|
---|
| 639 | Creates a hash_set with a copy of a range that's optimized for
|
---|
| 640 | holding up to <tt>n</tt> items, using <tt>h</tt> as the hash
|
---|
| 641 | function and <tt>k</tt> as the key equal function.
|
---|
| 642 | </TD>
|
---|
| 643 | </TR>
|
---|
| 644 |
|
---|
| 645 | <TR>
|
---|
| 646 | <TD VAlign=top>
|
---|
| 647 | <tt>dense_hash_set(const hash_set&)</tt>
|
---|
| 648 | </TD>
|
---|
| 649 | <TD VAlign=top>
|
---|
| 650 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
|
---|
| 651 | </TD>
|
---|
| 652 | <TD VAlign=top>
|
---|
| 653 | The copy constructor.
|
---|
| 654 | </TD>
|
---|
| 655 | </TR>
|
---|
| 656 |
|
---|
| 657 | <TR>
|
---|
| 658 | <TD VAlign=top>
|
---|
| 659 | <tt>dense_hash_set& operator=(const hash_set&)</tt>
|
---|
| 660 | </TD>
|
---|
| 661 | <TD VAlign=top>
|
---|
| 662 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
|
---|
| 663 | </TD>
|
---|
| 664 | <TD VAlign=top>
|
---|
| 665 | The assignment operator
|
---|
| 666 | </TD>
|
---|
| 667 | </TR>
|
---|
| 668 |
|
---|
| 669 | <TR>
|
---|
| 670 | <TD VAlign=top>
|
---|
| 671 | <tt>void swap(hash_set&)</tt>
|
---|
| 672 | </TD>
|
---|
| 673 | <TD VAlign=top>
|
---|
| 674 | <A href="http://www.sgi.com/tech/stl/Container.html">Container</A>
|
---|
| 675 | </TD>
|
---|
| 676 | <TD VAlign=top>
|
---|
| 677 | Swaps the contents of two hash_sets.
|
---|
| 678 | </TD>
|
---|
| 679 | </TR>
|
---|
| 680 |
|
---|
| 681 | <TR>
|
---|
| 682 | <TD VAlign=top>
|
---|
| 683 | <pre>pair<iterator, bool> insert(const value_type& x)
|
---|
| 684 | </pre>
|
---|
| 685 | </TD>
|
---|
| 686 | <TD VAlign=top>
|
---|
| 687 | <A
|
---|
| 688 | href="http://www.sgi.com/tech/stl/UniqueAssociativeContainer.html">Unique
|
---|
| 689 | Associative Container</A>
|
---|
| 690 | </TD>
|
---|
| 691 | <TD VAlign=top>
|
---|
| 692 | Inserts <tt>x</tt> into the <tt>dense_hash_set</tt>.
|
---|
| 693 | </TD>
|
---|
| 694 | </TR>
|
---|
| 695 |
|
---|
| 696 | <TR>
|
---|
| 697 | <TD VAlign=top>
|
---|
| 698 | <pre>template <class <A
|
---|
| 699 | href="http://www.sgi.com/tech/stl/InputIterator.html">InputIterator</A>>
|
---|
| 700 | void insert(InputIterator f, InputIterator l) </pre> <A href="#1">[2]</A>
|
---|
| 701 | </TD>
|
---|
| 702 | <TD VAlign=top>
|
---|
| 703 | <A
|
---|
| 704 | href="http://www.sgi.com/tech/stl/UniqueAssociativeContainer.html">Unique
|
---|
| 705 | Associative Container</A>
|
---|
| 706 | </TD>
|
---|
| 707 | <TD VAlign=top>
|
---|
| 708 | Inserts a range into the <tt>dense_hash_set</tt>.
|
---|
| 709 | </TD>
|
---|
| 710 | </TR>
|
---|
| 711 |
|
---|
| 712 | <TR>
|
---|
| 713 | <TD VAlign=top>
|
---|
| 714 | <tt>void set_empty_key(const key_type& key)</tt> <A href="#6">[6]</A>
|
---|
| 715 | </TD>
|
---|
| 716 | <TD VAlign=top>
|
---|
| 717 | <tt>dense_hash_set</tt>
|
---|
| 718 | </TD>
|
---|
| 719 | <TD VAlign=top>
|
---|
| 720 | See below.
|
---|
| 721 | </TD>
|
---|
| 722 | </TR>
|
---|
| 723 |
|
---|
| 724 | <TR>
|
---|
| 725 | <TD VAlign=top>
|
---|
| 726 | <tt>void set_deleted_key(const key_type& key)</tt> <A href="#6">[6]</A>
|
---|
| 727 | </TD>
|
---|
| 728 | <TD VAlign=top>
|
---|
| 729 | <tt>dense_hash_set</tt>
|
---|
| 730 | </TD>
|
---|
| 731 | <TD VAlign=top>
|
---|
| 732 | See below.
|
---|
| 733 | </TD>
|
---|
| 734 | </TR>
|
---|
| 735 |
|
---|
| 736 | <TR>
|
---|
| 737 | <TD VAlign=top>
|
---|
| 738 | <tt>void clear_deleted_key()</tt> <A href="#4">[6]</A>
|
---|
| 739 | </TD>
|
---|
| 740 | <TD VAlign=top>
|
---|
| 741 | <tt>dense_hash_set</tt>
|
---|
| 742 | </TD>
|
---|
| 743 | <TD VAlign=top>
|
---|
| 744 | See below.
|
---|
| 745 | </TD>
|
---|
| 746 | </TR>
|
---|
| 747 |
|
---|
| 748 | <TR>
|
---|
| 749 | <TD VAlign=top>
|
---|
| 750 | <tt>void erase(iterator pos)</tt>
|
---|
| 751 | </TD>
|
---|
| 752 | <TD VAlign=top>
|
---|
| 753 | <A
|
---|
| 754 | href="http://www.sgi.com/tech/stl/AssociativeContainer.html">Associative
|
---|
| 755 | Container</A>
|
---|
| 756 | </TD>
|
---|
| 757 | <TD VAlign=top>
|
---|
| 758 | Erases the element pointed to by <tt>pos</tt>.
|
---|
| 759 | <A href="#4">[6]</A>
|
---|
| 760 | </TD>
|
---|
| 761 | </TR>
|
---|
| 762 |
|
---|
| 763 | <TR>
|
---|
| 764 | <TD VAlign=top>
|
---|
| 765 | <tt>size_type erase(const key_type& k)</tt>
|
---|
| 766 | </TD>
|
---|
| 767 | <TD VAlign=top>
|
---|
| 768 | <A
|
---|
| 769 | href="http://www.sgi.com/tech/stl/AssociativeContainer.html">Associative
|
---|
| 770 | Container</A>
|
---|
| 771 | </TD>
|
---|
| 772 | <TD VAlign=top>
|
---|
| 773 | Erases the element whose key is <tt>k</tt>.
|
---|
| 774 | <A href="#4">[6]</A>
|
---|
| 775 | </TD>
|
---|
| 776 | </TR>
|
---|
| 777 |
|
---|
| 778 | <TR>
|
---|
| 779 | <TD VAlign=top>
|
---|
| 780 | <tt>void erase(iterator first, iterator last)</tt>
|
---|
| 781 | </TD>
|
---|
| 782 | <TD VAlign=top>
|
---|
| 783 | <A
|
---|
| 784 | href="http://www.sgi.com/tech/stl/AssociativeContainer.html">Associative
|
---|
| 785 | Container</A>
|
---|
| 786 | </TD>
|
---|
| 787 | <TD VAlign=top>
|
---|
| 788 | Erases all elements in a range.
|
---|
| 789 | <A href="#4">[6]</A>
|
---|
| 790 | </TD>
|
---|
| 791 | </TR>
|
---|
| 792 |
|
---|
| 793 | <TR>
|
---|
| 794 | <TD VAlign=top>
|
---|
| 795 | <tt>void clear()</tt>
|
---|
| 796 | </TD>
|
---|
| 797 | <TD VAlign=top>
|
---|
| 798 | <A
|
---|
| 799 | href="http://www.sgi.com/tech/stl/AssociativeContainer.html">Associative
|
---|
| 800 | Container</A>
|
---|
| 801 | </TD>
|
---|
| 802 | <TD VAlign=top>
|
---|
| 803 | Erases all of the elements.
|
---|
| 804 | </TD>
|
---|
| 805 | </TR>
|
---|
| 806 |
|
---|
| 807 | <TR>
|
---|
| 808 | <TD VAlign=top>
|
---|
| 809 | <tt>iterator find(const key_type& k) const</tt>
|
---|
| 810 | </TD>
|
---|
| 811 | <TD VAlign=top>
|
---|
| 812 | <A
|
---|
| 813 | href="http://www.sgi.com/tech/stl/AssociativeContainer.html">Associative
|
---|
| 814 | Container</A>
|
---|
| 815 | </TD>
|
---|
| 816 | <TD VAlign=top>
|
---|
| 817 | Finds an element whose key is <tt>k</tt>.
|
---|
| 818 | </TD>
|
---|
| 819 | </TR>
|
---|
| 820 |
|
---|
| 821 | <TR>
|
---|
| 822 | <TD VAlign=top>
|
---|
| 823 | <tt>size_type count(const key_type& k) const</tt>
|
---|
| 824 | </TD>
|
---|
| 825 | <TD VAlign=top>
|
---|
| 826 | <A
|
---|
| 827 | href="http://www.sgi.com/tech/stl/UniqueAssociativeContainer.html">Unique
|
---|
| 828 | Associative Container</A>
|
---|
| 829 | </TD>
|
---|
| 830 | <TD VAlign=top>
|
---|
| 831 | Counts the number of elements whose key is <tt>k</tt>.
|
---|
| 832 | </TD>
|
---|
| 833 | </TR>
|
---|
| 834 |
|
---|
| 835 | <TR>
|
---|
| 836 | <TD VAlign=top>
|
---|
| 837 | <pre>pair<iterator, iterator> equal_range(const
|
---|
| 838 | key_type& k) const</pre>
|
---|
| 839 | </TD>
|
---|
| 840 | <TD VAlign=top>
|
---|
| 841 | <A
|
---|
| 842 | href="http://www.sgi.com/tech/stl/AssociativeContainer.html">Associative
|
---|
| 843 | Container</A>
|
---|
| 844 | </TD>
|
---|
| 845 | <TD VAlign=top>
|
---|
| 846 | Finds a range containing all elements whose key is <tt>k</tt>.
|
---|
| 847 | </TD>
|
---|
| 848 | </TR>
|
---|
| 849 |
|
---|
| 850 | <TR>
|
---|
| 851 | <TD VAlign=top>
|
---|
| 852 | <tt>bool write_metadata(FILE *fp)</tt>
|
---|
| 853 | </TD>
|
---|
| 854 | <TD VAlign=top>
|
---|
| 855 | <tt>dense_hash_set</tt>
|
---|
| 856 | </TD>
|
---|
| 857 | <TD VAlign=top>
|
---|
| 858 | See below.
|
---|
| 859 | </TD>
|
---|
| 860 | </TR>
|
---|
| 861 |
|
---|
| 862 | <TR>
|
---|
| 863 | <TD VAlign=top>
|
---|
| 864 | <tt>bool read_metadata(FILE *fp)</tt>
|
---|
| 865 | </TD>
|
---|
| 866 | <TD VAlign=top>
|
---|
| 867 | <tt>dense_hash_set</tt>
|
---|
| 868 | </TD>
|
---|
| 869 | <TD VAlign=top>
|
---|
| 870 | See below.
|
---|
| 871 | </TD>
|
---|
| 872 | </TR>
|
---|
| 873 |
|
---|
| 874 | <TR>
|
---|
| 875 | <TD VAlign=top>
|
---|
| 876 | <tt>bool write_nopointer_data(FILE *fp)</tt>
|
---|
| 877 | </TD>
|
---|
| 878 | <TD VAlign=top>
|
---|
| 879 | <tt>dense_hash_set</tt>
|
---|
| 880 | </TD>
|
---|
| 881 | <TD VAlign=top>
|
---|
| 882 | See below.
|
---|
| 883 | </TD>
|
---|
| 884 | </TR>
|
---|
| 885 |
|
---|
| 886 | <TR>
|
---|
| 887 | <TD VAlign=top>
|
---|
| 888 | <tt>bool read_nopointer_data(FILE *fp)</tt>
|
---|
| 889 | </TD>
|
---|
| 890 | <TD VAlign=top>
|
---|
| 891 | <tt>dense_hash_set</tt>
|
---|
| 892 | </TD>
|
---|
| 893 | <TD VAlign=top>
|
---|
| 894 | See below.
|
---|
| 895 | </TD>
|
---|
| 896 | </TR>
|
---|
| 897 |
|
---|
| 898 | <TR>
|
---|
| 899 | <TD VAlign=top>
|
---|
| 900 | <pre>bool operator==(const hash_set&, const hash_set&)
|
---|
| 901 | </pre>
|
---|
| 902 | </TD>
|
---|
| 903 | <TD VAlign=top>
|
---|
| 904 | <A
|
---|
| 905 | href="http://www.sgi.com/tech/stl/HashedAssociativeContainer.html">Hashed
|
---|
| 906 | Associative Container</A>
|
---|
| 907 | </TD>
|
---|
| 908 | <TD VAlign=top>
|
---|
| 909 | Tests two hash_sets for equality. This is a global function, not a
|
---|
| 910 | member function.
|
---|
| 911 | </TD>
|
---|
| 912 | </TR>
|
---|
| 913 |
|
---|
| 914 | </table>
|
---|
| 915 |
|
---|
| 916 |
|
---|
| 917 | <h3>New members</h3>
|
---|
| 918 |
|
---|
| 919 | These members are not defined in the <A
|
---|
| 920 | href="http://www.sgi.com/tech/stl/UniqueHashedAssociativeContainer.html">Unique
|
---|
| 921 | Hashed Associative Container</A> and <A
|
---|
| 922 | href="http://www.sgi.com/tech/stl/SimpleAssociativeContainer.html">Simple
|
---|
| 923 | Associative Container</A> requirements, but are specific to
|
---|
| 924 | <tt>dense_hash_set</tt>.
|
---|
| 925 |
|
---|
| 926 | <table border>
|
---|
| 927 | <TR><TH>Member</TH><TH>Description</TH></TR>
|
---|
| 928 |
|
---|
| 929 | <TR>
|
---|
| 930 | <TD VAlign=top>
|
---|
| 931 | <tt>void set_empty_key(const key_type& key)</tt>
|
---|
| 932 | </TD>
|
---|
| 933 | <TD VAlign=top>
|
---|
| 934 | Sets the distinguished "empty" key to <tt>key</tt>. This must be
|
---|
| 935 | called immediately after construct time, before calls to another
|
---|
| 936 | other <tt>dense_hash_set</tt> operation. <A href="#6">[6]</A>
|
---|
| 937 | </TD>
|
---|
| 938 | </TR>
|
---|
| 939 |
|
---|
| 940 | <TR>
|
---|
| 941 | <TD VAlign=top>
|
---|
| 942 | <tt>void set_deleted_key(const key_type& key)</tt>
|
---|
| 943 | </TD>
|
---|
| 944 | <TD VAlign=top>
|
---|
| 945 | Sets the distinguished "deleted" key to <tt>key</tt>. This must be
|
---|
| 946 | called before any calls to <tt>erase()</tt>. <A href="#4">[6]</A>
|
---|
| 947 | </TD>
|
---|
| 948 | </TR>
|
---|
| 949 |
|
---|
| 950 | <TR>
|
---|
| 951 | <TD VAlign=top>
|
---|
| 952 | <tt>void clear_deleted_key()</tt> <A href="#4">[6]</A>
|
---|
| 953 | </TD>
|
---|
| 954 | <TD VAlign=top>
|
---|
| 955 | Clears the distinguished "deleted" key. After this is called,
|
---|
| 956 | calls to <tt>erase()</tt> are not valid on this object.
|
---|
| 957 | <A href="#4">[6]</A>
|
---|
| 958 | </TD>
|
---|
| 959 | </TR>
|
---|
| 960 |
|
---|
| 961 | <TR>
|
---|
| 962 | <TD VAlign=top>
|
---|
| 963 | <tt>bool write_metadata(FILE *fp)</tt>
|
---|
| 964 | </TD>
|
---|
| 965 | <TD VAlign=top>
|
---|
| 966 | Write hashtable metadata to <tt>fp</tt>. See <A HREF="#io">below</A>.
|
---|
| 967 | </TD>
|
---|
| 968 | </TR>
|
---|
| 969 |
|
---|
| 970 | <TR>
|
---|
| 971 | <TD VAlign=top>
|
---|
| 972 | <tt>bool read_metadata(FILE *fp)</tt>
|
---|
| 973 | </TD>
|
---|
| 974 | <TD VAlign=top>
|
---|
| 975 | Read hashtable metadata from <tt>fp</tt>. See <A HREF="#io">below</A>.
|
---|
| 976 | </TD>
|
---|
| 977 | </TR>
|
---|
| 978 |
|
---|
| 979 | <TR>
|
---|
| 980 | <TD VAlign=top>
|
---|
| 981 | <tt>bool write_nopointer_data(FILE *fp)</tt>
|
---|
| 982 | </TD>
|
---|
| 983 | <TD VAlign=top>
|
---|
| 984 | Write hashtable contents to <tt>fp</tt>. This is valid only if the
|
---|
| 985 | hashtable key and value are "plain" data. See <A HREF="#io">below</A>.
|
---|
| 986 | </TD>
|
---|
| 987 | </TR>
|
---|
| 988 |
|
---|
| 989 | <TR>
|
---|
| 990 | <TD VAlign=top>
|
---|
| 991 | <tt>bool read_nopointer_data(FILE *fp)</tt>
|
---|
| 992 | </TD>
|
---|
| 993 | <TD VAlign=top>
|
---|
| 994 | Read hashtable contents to <tt>fp</tt>. This is valid only if the
|
---|
| 995 | hashtable key and value are "plain" data. See <A HREF="#io">below</A>.
|
---|
| 996 | </TD>
|
---|
| 997 | </TR>
|
---|
| 998 |
|
---|
| 999 | </table>
|
---|
| 1000 |
|
---|
| 1001 |
|
---|
| 1002 | <h3>Notes</h3>
|
---|
| 1003 |
|
---|
| 1004 | <P><A name="1">[1]</A>
|
---|
| 1005 |
|
---|
| 1006 | This member function relies on <i>member template</i> functions, which
|
---|
| 1007 | may not be supported by all compilers. If your compiler supports
|
---|
| 1008 | member templates, you can call this function with any type of <A
|
---|
| 1009 | href="http://www.sgi.com/tech/stl/InputIterator.html">input
|
---|
| 1010 | iterator</A>. If your compiler does not yet support member templates,
|
---|
| 1011 | though, then the arguments must either be of type <tt>const
|
---|
| 1012 | value_type*</tt> or of type <tt>dense_hash_set::const_iterator</tt>.</p>
|
---|
| 1013 |
|
---|
| 1014 | <P><A name="2">[2]</A>
|
---|
| 1015 |
|
---|
| 1016 | In order to preserve iterators, erasing hashtable elements does not
|
---|
| 1017 | cause a hashtable to resize. This means that after a string of
|
---|
| 1018 | <tt>erase()</tt> calls, the hashtable will use more space than is
|
---|
| 1019 | required. At a cost of invalidating all current iterators, you can
|
---|
| 1020 | call <tt>resize()</tt> to manually compact the hashtable. The
|
---|
| 1021 | hashtable promotes too-small <tt>resize()</tt> arguments to the
|
---|
| 1022 | smallest legal value, so to compact a hashtable, it's sufficient to
|
---|
| 1023 | call <tt>resize(0)</tt>.
|
---|
| 1024 |
|
---|
| 1025 | <P><A name="3">[3]</A>
|
---|
| 1026 |
|
---|
| 1027 | Unlike some other hashtable implementations, the optional <i>n</i> in
|
---|
| 1028 | the constructor size indicates not the desired number of buckets that
|
---|
| 1029 | should be allocated, but instead the expected number of items to be
|
---|
| 1030 | inserted. The class then sizes the hash-set appropriately for the
|
---|
| 1031 | number of items specified. It's not an error to actually insert more
|
---|
| 1032 | or fewer items into the hashtable, but the implementation is most
|
---|
| 1033 | efficient -- does the fewest hashtable resizes -- if the number of
|
---|
| 1034 | inserted items is close to <i>n</i>.</p>
|
---|
| 1035 |
|
---|
| 1036 | <P><A name="4">[4]</A>
|
---|
| 1037 |
|
---|
| 1038 | <tt>dense_hash_set</tt> <b>requires</b> you call
|
---|
| 1039 | <tt>set_empty_key()</tt> immediately after constructing the hash-set,
|
---|
| 1040 | and before calling any other <tt>dense_hash_set</tt> method. (This is
|
---|
| 1041 | the largest difference between the <tt>dense_hash_set</tt> API and
|
---|
| 1042 | other hash-set APIs. See <A HREF="implementation.html">implementation.html</A>
|
---|
| 1043 | for why this is necessary.)
|
---|
| 1044 | The argument to <tt>set_empty_key()</tt> should be a key-value that
|
---|
| 1045 | is never used for legitimate hash-set entries. If you have no such
|
---|
| 1046 | key value, you will be unable to use <tt>dense_hash_set</tt>. It is
|
---|
| 1047 | an error to call <tt>insert()</tt> with an item whose key is the
|
---|
| 1048 | "empty key."</p>
|
---|
| 1049 |
|
---|
| 1050 | <tt>dense_hash_set</tt> also requires you call
|
---|
| 1051 | <tt>set_deleted_key()</tt> before calling <tt>erase()</tt>.
|
---|
| 1052 | The argument to <tt>set_deleted_key()</tt> should be a key-value that
|
---|
| 1053 | is never used for legitimate hash-set entries. It must be different
|
---|
| 1054 | from the key-value used for <tt>set_empty_key()</tt>. It is an error to call
|
---|
| 1055 | <tt>erase()</tt> without first calling <tt>set_deleted_key()</tt>, and
|
---|
| 1056 | it is also an error to call <tt>insert()</tt> with an item whose key
|
---|
| 1057 | is the "deleted key."</p>
|
---|
| 1058 |
|
---|
| 1059 | <p>There is no need to call <tt>set_deleted_key</tt> if you do not
|
---|
| 1060 | wish to call <tt>erase()</tt> on the hash-set.</p>
|
---|
| 1061 |
|
---|
| 1062 | <p>It is acceptable to change the deleted-key at any time by calling
|
---|
| 1063 | <tt>set_deleted_key()</tt> with a new argument. You can also call
|
---|
| 1064 | <tt>clear_deleted_key()</tt>, at which point all keys become valid for
|
---|
| 1065 | insertion but no hashtable entries can be deleted until
|
---|
| 1066 | <tt>set_deleted_key()</tt> is called again.</p>
|
---|
| 1067 |
|
---|
| 1068 | <P><A name="5">[5]</A>
|
---|
| 1069 |
|
---|
| 1070 | Both <tt>key_type</tt> and <tt>data_type</tt> must be <A
|
---|
| 1071 | HREF="http://c2.com/cgi/wiki?PlainOldData">plain old data</A> (see
|
---|
| 1072 | <A HREF="implementation.html">implementation.html</A> for why this is
|
---|
| 1073 | necessary). In addition, there should
|
---|
| 1074 | be no data structures that point directly into parts of key or value,
|
---|
| 1075 | including the key or value itself (for instance, you cannot have a
|
---|
| 1076 | value like <tt>struct {int a = 1, *b = &a}</tt>. This is because
|
---|
| 1077 | <tt>dense_hash_set</tt> uses <tt>malloc()</tt> and <tt>free()</tt> to
|
---|
| 1078 | allocate space for the key and value, and <tt>memmove()</tt> to
|
---|
| 1079 | reorganize the key and value in memory.</p>
|
---|
| 1080 |
|
---|
| 1081 | <p>Almost all common uses fit this criterion: <tt>key_type</tt> can be
|
---|
| 1082 | a basic C type or an STL type like <tt>string</tt>, for instance. If
|
---|
| 1083 | <tt>value_type</tt> is complex, consider storing only the pointer to
|
---|
| 1084 | the data in the <tt>dense_hash_set</tt>. This will speed up the
|
---|
| 1085 | hashtable as well, since hashtable resizes will have to manipulate
|
---|
| 1086 | less memory.</p>
|
---|
| 1087 |
|
---|
| 1088 |
|
---|
| 1089 | <h3><A NAME=io>Input/Output</A></h3>
|
---|
| 1090 |
|
---|
| 1091 | <table border=1 cellpadding=5><tr><td>
|
---|
| 1092 | <p><b>IMPORTANT IMPLEMENTATION NOTE:</b> In the current version of
|
---|
| 1093 | this code, the input/output routines for <tt>dense_hash_set</tt> have
|
---|
| 1094 | <b>not yet been implemented</b>. This section explains the API, but
|
---|
| 1095 | note that all calls to these routines will fail (return
|
---|
| 1096 | <tt>false</tt>). It is a TODO to remedy this situation.</p>
|
---|
| 1097 | </td></tr></table>
|
---|
| 1098 |
|
---|
| 1099 | <p>It is possible to save and restore <tt>dense_hash_set</tt> objects
|
---|
| 1100 | to disk. Storage takes place in two steps. The first writes the
|
---|
| 1101 | hashtable metadata. The second writes the actual data.</p>
|
---|
| 1102 |
|
---|
| 1103 | <p>To write a hashtable to disk, first call <tt>write_metadata()</tt>
|
---|
| 1104 | on an open file pointer. This saves the hashtable information in a
|
---|
| 1105 | byte-order-independent format.</p>
|
---|
| 1106 |
|
---|
| 1107 | <p>After the metadata has been written to disk, you must write the
|
---|
| 1108 | actual data stored in the hash-set to disk. If both the key and data
|
---|
| 1109 | are "simple" enough, you can do this by calling
|
---|
| 1110 | <tt>write_nopointer_data()</tt>. "Simple" data is data that can be
|
---|
| 1111 | safely copied to disk via <tt>fwrite()</tt>. Native C data types fall
|
---|
| 1112 | into this category, as do structs of native C data types. Pointers
|
---|
| 1113 | and STL objects do not.</p>
|
---|
| 1114 |
|
---|
| 1115 | <p>Note that <tt>write_nopointer_data()</tt> does not do any endian
|
---|
| 1116 | conversion. Thus, it is only appropriate when you intend to read the
|
---|
| 1117 | data on the same endian architecture as you write the data.</p>
|
---|
| 1118 |
|
---|
| 1119 | <p>If you cannot use <tt>write_nopointer_data()</tt> for any reason,
|
---|
| 1120 | you can write the data yourself by iterating over the
|
---|
| 1121 | <tt>dense_hash_set</tt> with a <tt>const_iterator</tt> and writing
|
---|
| 1122 | the key and data in any manner you wish.</p>
|
---|
| 1123 |
|
---|
| 1124 | <p>To read the hashtable information from disk, first you must create
|
---|
| 1125 | a <tt>dense_hash_set</tt> object. Then open a file pointer to point
|
---|
| 1126 | to the saved hashtable, and call <tt>read_metadata()</tt>. If you
|
---|
| 1127 | saved the data via <tt>write_nopointer_data()</tt>, you can follow the
|
---|
| 1128 | <tt>read_metadata()</tt> call with a call to
|
---|
| 1129 | <tt>read_nopointer_data()</tt>. This is all that is needed.</p>
|
---|
| 1130 |
|
---|
| 1131 | <p>If you saved the data through a custom write routine, you must call
|
---|
| 1132 | a custom read routine to read in the data. To do this, iterate over
|
---|
| 1133 | the <tt>dense_hash_set</tt> with an <tt>iterator</tt>; this operation
|
---|
| 1134 | is sensical because the metadata has already been set up. For each
|
---|
| 1135 | iterator item, you can read the key and value from disk, and set it
|
---|
| 1136 | appropriately. You will need to do a <tt>const_cast</tt> on the
|
---|
| 1137 | iterator, since <tt>it->first</tt> is always <tt>const</tt>. The
|
---|
| 1138 | code might look like this:</p>
|
---|
| 1139 | <pre>
|
---|
| 1140 | for (dense_hash_set<int*, int>::iterator it = ht.begin();
|
---|
| 1141 | it != ht.end(); ++it) {
|
---|
| 1142 | const_cast<int*>(it->first) = new int;
|
---|
| 1143 | fread(const_cast<int*>(it->first), sizeof(int), 1, fp);
|
---|
| 1144 | fread(&it->second, sizeof(int), 1, fp);
|
---|
| 1145 | }
|
---|
| 1146 | </pre>
|
---|
| 1147 |
|
---|
| 1148 |
|
---|
| 1149 | <h3><A NAME=iter>Validity of Iterators</A></h3>
|
---|
| 1150 |
|
---|
| 1151 | <p><tt>insert()</tt> invalidates all iterators, as does
|
---|
| 1152 | <tt>resize()</tt>. <tt>erase()</tt> is guaranteed not to invalidate
|
---|
| 1153 | any iterators.</p>
|
---|
| 1154 |
|
---|
| 1155 | <p>This is implemented by making <tt>erase()</tt> not resize the
|
---|
| 1156 | hashtable. If you desire maximum space efficiency, you can call
|
---|
| 1157 | <tt>resize(0)</tt> after a string of <tt>erase()</tt> calls, to force
|
---|
| 1158 | the hashtable to resize to the smallest possible size.</p>
|
---|
| 1159 |
|
---|
| 1160 |
|
---|
| 1161 | <h3>See also</h3>
|
---|
| 1162 |
|
---|
| 1163 | <p>The following are SGI STL concepts and classes related to
|
---|
| 1164 | <tt>dense_hash_set</tt>.</p>
|
---|
| 1165 |
|
---|
| 1166 | <tt><A href="http://www.sgi.com/tech/stl/hash_set.html">hash_set</A></tt>,
|
---|
| 1167 | <A href="http://www.sgi.com/tech/stl/AssociativeContainer.html">Associative Container</A>,
|
---|
| 1168 | <A href="http://www.sgi.com/tech/stl/HashedAssociativeContainer.html">Hashed Associative Container</A>,
|
---|
| 1169 | <A href="http://www.sgi.com/tech/stl/SimpleAssociativeContainer.html">Simple Associative Container</A>,
|
---|
| 1170 | <A href="http://www.sgi.com/tech/stl/UniqueHashedAssociativeContainer.html">Unique Hashed Associative Container</A>,
|
---|
| 1171 | <tt><A href="http://www.sgi.com/tech/stl/set.html">set</A></tt>,
|
---|
| 1172 | <tt><A href="http://www.sgi.com/tech/stl/Map.html">map</A></tt>
|
---|
| 1173 | <tt><A href="http://www.sgi.com/tech/stl/multiset.html">multiset</A></tt>,
|
---|
| 1174 | <tt><A href="http://www.sgi.com/tech/stl/Multimap.html">multimap</A></tt>,
|
---|
| 1175 | <tt><A href="http://www.sgi.com/tech/stl/hash_map.html">hash_map</A></tt>,
|
---|
| 1176 | <tt><A href="http://www.sgi.com/tech/stl/hash_multiset.html">hash_multiset</A></tt>,
|
---|
| 1177 | <tt><A href="http://www.sgi.com/tech/stl/hash_multimap.html">hash_multimap</A></tt>,
|
---|
| 1178 | <tt><A href="sparse_hash_set.html">sparse_hash_set</A></tt>,
|
---|
| 1179 | <tt><A href="sparse_hash_map.html">sparse_hash_map</A></tt>,
|
---|
| 1180 | <tt><A href="dense_hash_map.html">dense_hash_map</A></tt>
|
---|
| 1181 |
|
---|
| 1182 | </BODY>
|
---|
| 1183 | </HTML>
|
---|