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diff --git a/libstdc++-v3/doc/html/ext/pb_ds/concepts.html b/libstdc++-v3/doc/html/ext/pb_ds/concepts.html new file mode 100644 index 000000000..9f6c22462 --- /dev/null +++ b/libstdc++-v3/doc/html/ext/pb_ds/concepts.html @@ -0,0 +1,118 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> + +<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> +<head> + <meta name="generator" content= + "HTML Tidy for Linux/x86 (vers 12 April 2005), see www.w3.org" /> + + <title>Concepts</title> + <meta http-equiv="Content-Type" content= + "text/html; charset=us-ascii" /> + </head> + +<body> + <div id="page"> + <h1>Concepts</h1> + + <h2><a name="concepts_find_and_range_iterators" id= + "concepts_find_and_range_iterators">Point and Range Methods and + Iterators</a></h2> + + <p>A point-type iterator is an iterator that refers to a + specific element, <i>e.g.</i> as returned through an + associative-container's <tt>find</tt> method; a range-type + iterator is an iterator that is used to go over a sequence of + elements, <i>e.g.</i>, as returned by a container's + <tt>find</tt> method. A point-type method is a method that + returns a point-type iterator; a range-type method is a method + that returns a range-type iterator.</p> + + <p>For most containers, these types are synonymous; for + self-organizing containers, such as hash-based containers or + priority queues, these are inherently different (in any + implementation, including that of the STL), but in + <tt>pb_ds</tt> this is made explicit - they are distinct + types.</p> + + + <h2><a name="invalidation_guarantees" id= + "invalidation_guarantees">Invalidation Guarantees</a></h2> + + <p>If one manipulates a container object, then iterators + previously obtained from it can be invalidated. In some cases a + previously-obtained iterator cannot be de-referenced; in other + cases, the iterator's next or previous element might have + changed unpredictably. This corresponds exactly to the question + whether a point-type or range-type iterator (see previous + concept) is valid or not. In <tt>pb_ds</tt> one can query a + container (in compile time) what are its invalidation + guarantees.</p> + + <h2><a name="prm_sec" id="prm_sec">Primary and Secondary Keys + and Associative Containers</a></h2> + + <p>In <tt>pb_ds</tt> there are no associative containers which + allow multiple values with equivalent keys (such as the STL's + <tt>std::multimap</tt>, for example). Instead, one maps the + unique part of a key - the primary key, into an + associative-container of the (originally) non-unique parts of + the key - the secondary key. A primary associative-container is + an associative container of primary keys; a secondary + associative-container is an associative container of secondary + keys.</p> + + + <h2><a name="concepts_null_policies" id= + "concepts_null_policies">Null Policy Classes</a></h2> + + <p>Associative containers are typically parametrized by + various policies. For example, a hash-based associative + container is parametrized by a hash-functor, transforming each + key into an non-negative numerical type. Each such value is + then further mapped into a position within the table. The + mapping of a key into a position within the table is therefore + a two-step process.</p> + + <p>In some cases, instantiations are <i>redundant</i>. For + example, when the keys are integers, it is possible to use a + <i>redundant</i> hash policy, which transforms each key into + its value.</p> + + <p>In some other cases, these policies are <i>irrelevant</i>. + For example, a hash-based associative container might transform + keys into positions within a table by a different method than + the two-step method described above. In such a case, the hash + functor is simply irrelevant.</p> + + <p><tt>pb_ds</tt> uses special pre-defined "null policies" + classes for these cases. Some null policies in <tt>pb_ds</tt> + are:</p> + + <ol> + <li><a href= + "null_mapped_type.html"><tt>null_mapped_type</tt></a></li> + + <li><a href= + "null_tree_node_update.html"><tt>null_tree_node_update</tt></a></li> + + <li><a href= + "null_trie_node_update.html"><tt>null_trie_node_update</tt></a></li> + + <li><a href= + "null_hash_fn.html"><tt>null_hash_fn</tt></a></li> + + <li><a href= + "null_probe_fn.html"><tt>null_probe_fn</tt></a></li> + </ol> + + <p>A "set" in <tt>pb_ds</tt>, for example, is an associative + container with its <tt>Data_Parameter</tt> instantiated by + <a href="null_mapped_type.html"><tt>null_mapped_type</tt></a>. + <a href= + "tree_based_containers.html#invariants">Design::Tree-Based + Containers::Node Invariants</a> explains another case where a + null policy is needed.</p> + </div> +</body> +</html> |