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diff --git a/gcc-4.4.3/libstdc++-v3/doc/xml/manual/containers.xml b/gcc-4.4.3/libstdc++-v3/doc/xml/manual/containers.xml deleted file mode 100644 index 2b29ba6fc..000000000 --- a/gcc-4.4.3/libstdc++-v3/doc/xml/manual/containers.xml +++ /dev/null @@ -1,450 +0,0 @@ -<?xml version='1.0'?> -<!DOCTYPE part PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" - "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" -[ ]> - -<part id="manual.containers" xreflabel="Containers"> -<?dbhtml filename="containers.html"?> - -<partinfo> - <keywordset> - <keyword> - ISO C++ - </keyword> - <keyword> - library - </keyword> - </keywordset> -</partinfo> - -<title> - Containers - <indexterm><primary>Containers</primary></indexterm> -</title> - -<!-- Chapter 01 : Sequences --> -<chapter id="manual.containers.sequences" xreflabel="Sequences"> -<?dbhtml filename="sequences.html"?> - <title>Sequences</title> - -<sect1 id="containers.sequences.list" xreflabel="list"> -<?dbhtml filename="list.html"?> - <title>list</title> - <sect2 id="sequences.list.size" xreflabel="list::size() is O(n)"> - <title>list::size() is O(n)</title> - <para> - Yes it is, and that's okay. This is a decision that we preserved - when we imported SGI's STL implementation. The following is - quoted from <ulink - url="http://www.sgi.com/tech/stl/FAQ.html">their FAQ</ulink>: - </para> - <blockquote> - <para> - The size() member function, for list and slist, takes time - proportional to the number of elements in the list. This was a - deliberate tradeoff. The only way to get a constant-time - size() for linked lists would be to maintain an extra member - variable containing the list's size. This would require taking - extra time to update that variable (it would make splice() a - linear time operation, for example), and it would also make the - list larger. Many list algorithms don't require that extra - word (algorithms that do require it might do better with - vectors than with lists), and, when it is necessary to maintain - an explicit size count, it's something that users can do - themselves. - </para> - <para> - This choice is permitted by the C++ standard. The standard says - that size() <quote>should</quote> be constant time, and - <quote>should</quote> does not mean the same thing as - <quote>shall</quote>. This is the officially recommended ISO - wording for saying that an implementation is supposed to do - something unless there is a good reason not to. - </para> - <para> - One implication of linear time size(): you should never write - </para> - <programlisting> - if (L.size() == 0) - ... - </programlisting> - - <para> - Instead, you should write - </para> - - <programlisting> - if (L.empty()) - ... - </programlisting> - </blockquote> - </sect2> -</sect1> - -<sect1 id="containers.sequences.vector" xreflabel="vector"> -<?dbhtml filename="vector.html"?> - <title>vector</title> - <para> - </para> - <sect2 id="sequences.vector.management" xreflabel="Space Overhead Management"> - <title>Space Overhead Management</title> - <para> - In <ulink - url="http://gcc.gnu.org/ml/libstdc++/2002-04/msg00105.html">this - message to the list</ulink>, Daniel Kostecky announced work on an - alternate form of <code>std::vector</code> that would support - hints on the number of elements to be over-allocated. The design - was also described, along with possible implementation choices. - </para> - <para> - The first two alpha releases were announced <ulink - url="http://gcc.gnu.org/ml/libstdc++/2002-07/msg00048.html">here</ulink> - and <ulink - url="http://gcc.gnu.org/ml/libstdc++/2002-07/msg00111.html">here</ulink>. - The releases themselves are available at - <ulink url="http://www.kotelna.sk/dk/sw/caphint/"> - http://www.kotelna.sk/dk/sw/caphint/</ulink>. - </para> - - </sect2></sect1> -</chapter> - -<!-- Chapter 02 : Associative --> -<chapter id="manual.containers.associative" xreflabel="Associative"> -<?dbhtml filename="associative.html"?> - <title>Associative</title> - - <sect1 id="containers.associative.insert_hints" xreflabel="Insertion Hints"> - <title>Insertion Hints</title> - <para> - Section [23.1.2], Table 69, of the C++ standard lists this - function for all of the associative containers (map, set, etc): - </para> - <programlisting> - a.insert(p,t); - </programlisting> - <para> - where 'p' is an iterator into the container 'a', and 't' is the - item to insert. The standard says that <quote><code>t</code> is - inserted as close as possible to the position just prior to - <code>p</code>.</quote> (Library DR #233 addresses this topic, - referring to <ulink - url='http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1780.html'>N1780</ulink>. - Since version 4.2 GCC implements the resolution to DR 233, so - that insertions happen as close as possible to the hint. For - earlier releases the hint was only used as described below. - </para> - <para> - Here we'll describe how the hinting works in the libstdc++ - implementation, and what you need to do in order to take - advantage of it. (Insertions can change from logarithmic - complexity to amortized constant time, if the hint is properly - used.) Also, since the current implementation is based on the - SGI STL one, these points may hold true for other library - implementations also, since the HP/SGI code is used in a lot of - places. - </para> - <para> - In the following text, the phrases <emphasis>greater - than</emphasis> and <emphasis>less than</emphasis> refer to the - results of the strict weak ordering imposed on the container by - its comparison object, which defaults to (basically) - <quote><</quote>. Using those phrases is semantically sloppy, - but I didn't want to get bogged down in syntax. I assume that if - you are intelligent enough to use your own comparison objects, - you are also intelligent enough to assign <quote>greater</quote> - and <quote>lesser</quote> their new meanings in the next - paragraph. *grin* - </para> - <para> - If the <code>hint</code> parameter ('p' above) is equivalent to: - </para> - <itemizedlist> - <listitem> - <para> - <code>begin()</code>, then the item being inserted should - have a key less than all the other keys in the container. - The item will be inserted at the beginning of the container, - becoming the new entry at <code>begin()</code>. - </para> - </listitem> - <listitem> - <para> - <code>end()</code>, then the item being inserted should have - a key greater than all the other keys in the container. The - item will be inserted at the end of the container, becoming - the new entry at <code>end()</code>. - </para> - </listitem> - <listitem> - <para> - neither <code>begin()</code> nor <code>end()</code>, then: - Let <code>h</code> be the entry in the container pointed to - by <code>hint</code>, that is, <code>h = *hint</code>. Then - the item being inserted should have a key less than that of - <code>h</code>, and greater than that of the item preceding - <code>h</code>. The new item will be inserted between - <code>h</code> and <code>h</code>'s predecessor. - </para> - </listitem> - </itemizedlist> - <para> - For <code>multimap</code> and <code>multiset</code>, the - restrictions are slightly looser: <quote>greater than</quote> - should be replaced by <quote>not less than</quote>and <quote>less - than</quote> should be replaced by <quote>not greater - than.</quote> (Why not replace greater with - greater-than-or-equal-to? You probably could in your head, but - the mathematicians will tell you that it isn't the same thing.) - </para> - <para> - If the conditions are not met, then the hint is not used, and the - insertion proceeds as if you had called <code> a.insert(t) - </code> instead. (<emphasis>Note </emphasis> that GCC releases - prior to 3.0.2 had a bug in the case with <code>hint == - begin()</code> for the <code>map</code> and <code>set</code> - classes. You should not use a hint argument in those releases.) - </para> - <para> - This behavior goes well with other containers' - <code>insert()</code> functions which take an iterator: if used, - the new item will be inserted before the iterator passed as an - argument, same as the other containers. - </para> - <para> - <emphasis>Note </emphasis> also that the hint in this - implementation is a one-shot. The older insertion-with-hint - routines check the immediately surrounding entries to ensure that - the new item would in fact belong there. If the hint does not - point to the correct place, then no further local searching is - done; the search begins from scratch in logarithmic time. - </para> - </sect1> - - - <sect1 id="containers.associative.bitset" xreflabel="bitset"> - <?dbhtml filename="bitset.html"?> - <title>bitset</title> - <sect2 id="associative.bitset.size_variable" xreflabel="Variable"> - <title>Size Variable</title> - <para> - No, you cannot write code of the form - </para> - <!-- Careful, the leading spaces in PRE show up directly. --> - <programlisting> - #include <bitset> - - void foo (size_t n) - { - std::bitset<n> bits; - .... - } - </programlisting> - <para> - because <code>n</code> must be known at compile time. Your - compiler is correct; it is not a bug. That's the way templates - work. (Yes, it <emphasis>is</emphasis> a feature.) - </para> - <para> - There are a couple of ways to handle this kind of thing. Please - consider all of them before passing judgement. They include, in - no particular order: - </para> - <itemizedlist> - <listitem><para>A very large N in <code>bitset<N></code>.</para></listitem> - <listitem><para>A container<bool>.</para></listitem> - <listitem><para>Extremely weird solutions.</para></listitem> - </itemizedlist> - <para> - <emphasis>A very large N in - <code>bitset<N></code>. </emphasis> It has been - pointed out a few times in newsgroups that N bits only takes up - (N/8) bytes on most systems, and division by a factor of eight is - pretty impressive when speaking of memory. Half a megabyte given - over to a bitset (recall that there is zero space overhead for - housekeeping info; it is known at compile time exactly how large - the set is) will hold over four million bits. If you're using - those bits as status flags (e.g., - <quote>changed</quote>/<quote>unchanged</quote> flags), that's a - <emphasis>lot</emphasis> of state. - </para> - <para> - You can then keep track of the <quote>maximum bit used</quote> - during some testing runs on representative data, make note of how - many of those bits really need to be there, and then reduce N to - a smaller number. Leave some extra space, of course. (If you - plan to write code like the incorrect example above, where the - bitset is a local variable, then you may have to talk your - compiler into allowing that much stack space; there may be zero - space overhead, but it's all allocated inside the object.) - </para> - <para> - <emphasis>A container<bool>. </emphasis> The - Committee made provision for the space savings possible with that - (N/8) usage previously mentioned, so that you don't have to do - wasteful things like <code>Container<char></code> or - <code>Container<short int></code>. Specifically, - <code>vector<bool></code> is required to be specialized for - that space savings. - </para> - <para> - The problem is that <code>vector<bool></code> doesn't - behave like a normal vector anymore. There have been recent - journal articles which discuss the problems (the ones by Herb - Sutter in the May and July/August 1999 issues of C++ Report cover - it well). Future revisions of the ISO C++ Standard will change - the requirement for <code>vector<bool></code> - specialization. In the meantime, <code>deque<bool></code> - is recommended (although its behavior is sane, you probably will - not get the space savings, but the allocation scheme is different - than that of vector). - </para> - <para> - <emphasis>Extremely weird solutions. </emphasis> If - you have access to the compiler and linker at runtime, you can do - something insane, like figuring out just how many bits you need, - then writing a temporary source code file. That file contains an - instantiation of <code>bitset</code> for the required number of - bits, inside some wrapper functions with unchanging signatures. - Have your program then call the compiler on that file using - Position Independent Code, then open the newly-created object - file and load those wrapper functions. You'll have an - instantiation of <code>bitset<N></code> for the exact - <code>N</code> that you need at the time. Don't forget to delete - the temporary files. (Yes, this <emphasis>can</emphasis> be, and - <emphasis>has been</emphasis>, done.) - </para> - <!-- I wonder if this next paragraph will get me in trouble... --> - <para> - This would be the approach of either a visionary genius or a - raving lunatic, depending on your programming and management - style. Probably the latter. - </para> - <para> - Which of the above techniques you use, if any, are up to you and - your intended application. Some time/space profiling is - indicated if it really matters (don't just guess). And, if you - manage to do anything along the lines of the third category, the - author would love to hear from you... - </para> - <para> - Also note that the implementation of bitset used in libstdc++ has - <ulink url="../ext/sgiexts.html#ch23">some extensions</ulink>. - </para> - - </sect2> - <sect2 id="associative.bitset.type_string" xreflabel="Type String"> - <title>Type String</title> - <para> - </para> - <para> - Bitmasks do not take char* nor const char* arguments in their - constructors. This is something of an accident, but you can read - about the problem: follow the library's <quote>Links</quote> from - the homepage, and from the C++ information <quote>defect - reflector</quote> link, select the library issues list. Issue - number 116 describes the problem. - </para> - <para> - For now you can simply make a temporary string object using the - constructor expression: - </para> - <programlisting> - std::bitset<5> b ( std::string(<quote>10110</quote>) ); - </programlisting> - - <para> - instead of - </para> - - <programlisting> - std::bitset<5> b ( <quote>10110</quote> ); // invalid - </programlisting> - </sect2> - </sect1> - -</chapter> - -<!-- Chapter 03 : Interacting with C --> -<chapter id="manual.containers.c" xreflabel="Interacting with C"> -<?dbhtml filename="containers_and_c.html"?> - <title>Interacting with C</title> - - <sect1 id="containers.c.vs_array" xreflabel="Containers vs. Arrays"> - <title>Containers vs. Arrays</title> - <para> - You're writing some code and can't decide whether to use builtin - arrays or some kind of container. There are compelling reasons - to use one of the container classes, but you're afraid that - you'll eventually run into difficulties, change everything back - to arrays, and then have to change all the code that uses those - data types to keep up with the change. - </para> - <para> - If your code makes use of the standard algorithms, this isn't as - scary as it sounds. The algorithms don't know, nor care, about - the kind of <quote>container</quote> on which they work, since - the algorithms are only given endpoints to work with. For the - container classes, these are iterators (usually - <code>begin()</code> and <code>end()</code>, but not always). - For builtin arrays, these are the address of the first element - and the <ulink - url="../24_iterators/howto.html#2">past-the-end</ulink> element. - </para> - <para> - Some very simple wrapper functions can hide all of that from the - rest of the code. For example, a pair of functions called - <code>beginof</code> can be written, one that takes an array, - another that takes a vector. The first returns a pointer to the - first element, and the second returns the vector's - <code>begin()</code> iterator. - </para> - <para> - The functions should be made template functions, and should also - be declared inline. As pointed out in the comments in the code - below, this can lead to <code>beginof</code> being optimized out - of existence, so you pay absolutely nothing in terms of increased - code size or execution time. - </para> - <para> - The result is that if all your algorithm calls look like - </para> - <programlisting> - std::transform(beginof(foo), endof(foo), beginof(foo), SomeFunction); - </programlisting> - <para> - then the type of foo can change from an array of ints to a vector - of ints to a deque of ints and back again, without ever changing - any client code. - </para> - <para> - This author has a collection of such functions, called - <quote>*of</quote> because they all extend the builtin - <quote>sizeof</quote>. It started with some Usenet discussions - on a transparent way to find the length of an array. A - simplified and much-reduced version for easier reading is <ulink - url="wrappers_h.txt">given here</ulink>. - </para> - <para> - Astute readers will notice two things at once: first, that the - container class is still a <code>vector<T></code> instead - of a more general <code>Container<T></code>. This would - mean that three functions for <code>deque</code> would have to be - added, another three for <code>list</code>, and so on. This is - due to problems with getting template resolution correct; I find - it easier just to give the extra three lines and avoid confusion. - </para> - <para> - Second, the line - </para> - <programlisting> - inline unsigned int lengthof (T (&)[sz]) { return sz; } - </programlisting> - <para> - looks just weird! Hint: unused parameters can be left nameless. - </para> - </sect1> - -</chapter> - -</part> |