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diff --git a/gcc-4.8.1/libstdc++-v3/doc/html/manual/associative.html b/gcc-4.8.1/libstdc++-v3/doc/html/manual/associative.html deleted file mode 100644 index 21b01044d..000000000 --- a/gcc-4.8.1/libstdc++-v3/doc/html/manual/associative.html +++ /dev/null @@ -1,191 +0,0 @@ -<?xml version="1.0" encoding="UTF-8" standalone="no"?> -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Associative</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.77.1" /><meta name="keywords" content="ISO C++, library" /><meta name="keywords" content="ISO C++, runtime, library" /><link rel="home" href="../index.html" title="The GNU C++ Library" /><link rel="up" href="containers.html" title="Chapter 9. Containers" /><link rel="prev" href="containers.html" title="Chapter 9. Containers" /><link rel="next" href="unordered_associative.html" title="Unordered Associative" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Associative</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="containers.html">Prev</a> </td><th width="60%" align="center">Chapter 9. - Containers - -</th><td width="20%" align="right"> <a accesskey="n" href="unordered_associative.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="std.containers.associative"></a>Associative</h2></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="containers.associative.insert_hints"></a>Insertion Hints</h3></div></div></div><p> - Section [23.1.2], Table 69, of the C++ standard lists this - function for all of the associative containers (map, set, etc): - </p><pre class="programlisting"> - a.insert(p,t); - </pre><p> - where 'p' is an iterator into the container 'a', and 't' is the - item to insert. The standard says that <span class="quote">“<span class="quote"><code class="code">t</code> is - inserted as close as possible to the position just prior to - <code class="code">p</code>.</span>”</span> (Library DR #233 addresses this topic, - referring to <a class="link" href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1780.html" target="_top">N1780</a>. - 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. - </p><p> - 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. - </p><p> - In the following text, the phrases <span class="emphasis"><em>greater - than</em></span> and <span class="emphasis"><em>less than</em></span> refer to the - results of the strict weak ordering imposed on the container by - its comparison object, which defaults to (basically) - <span class="quote">“<span class="quote"><</span>”</span>. 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 <span class="quote">“<span class="quote">greater</span>”</span> - and <span class="quote">“<span class="quote">lesser</span>”</span> their new meanings in the next - paragraph. *grin* - </p><p> - If the <code class="code">hint</code> parameter ('p' above) is equivalent to: - </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p> - <code class="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 class="code">begin()</code>. - </p></li><li class="listitem"><p> - <code class="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 before <code class="code">end()</code>. - </p></li><li class="listitem"><p> - neither <code class="code">begin()</code> nor <code class="code">end()</code>, then: - Let <code class="code">h</code> be the entry in the container pointed to - by <code class="code">hint</code>, that is, <code class="code">h = *hint</code>. Then - the item being inserted should have a key less than that of - <code class="code">h</code>, and greater than that of the item preceding - <code class="code">h</code>. The new item will be inserted between - <code class="code">h</code> and <code class="code">h</code>'s predecessor. - </p></li></ul></div><p> - For <code class="code">multimap</code> and <code class="code">multiset</code>, the - restrictions are slightly looser: <span class="quote">“<span class="quote">greater than</span>”</span> - should be replaced by <span class="quote">“<span class="quote">not less than</span>”</span>and <span class="quote">“<span class="quote">less - than</span>”</span> should be replaced by <span class="quote">“<span class="quote">not greater - than.</span>”</span> (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.) - </p><p> - If the conditions are not met, then the hint is not used, and the - insertion proceeds as if you had called <code class="code"> a.insert(t) - </code> instead. (<span class="emphasis"><em>Note </em></span> that GCC releases - prior to 3.0.2 had a bug in the case with <code class="code">hint == - begin()</code> for the <code class="code">map</code> and <code class="code">set</code> - classes. You should not use a hint argument in those releases.) - </p><p> - This behavior goes well with other containers' - <code class="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. - </p><p> - <span class="emphasis"><em>Note </em></span> 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. - </p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="containers.associative.bitset"></a>bitset</h3></div></div></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="associative.bitset.size_variable"></a>Size Variable</h4></div></div></div><p> - No, you cannot write code of the form - </p><pre class="programlisting"> - #include <bitset> - - void foo (size_t n) - { - std::bitset<n> bits; - .... - } - </pre><p> - because <code class="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 <span class="emphasis"><em>is</em></span> a feature.) - </p><p> - There are a couple of ways to handle this kind of thing. Please - consider all of them before passing judgement. They include, in - no chaptericular order: - </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>A very large N in <code class="code">bitset<N></code>.</p></li><li class="listitem"><p>A container<bool>.</p></li><li class="listitem"><p>Extremely weird solutions.</p></li></ul></div><p> - <span class="emphasis"><em>A very large N in - <code class="code">bitset<N></code>. </em></span> 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., - <span class="quote">“<span class="quote">changed</span>”</span>/<span class="quote">“<span class="quote">unchanged</span>”</span> flags), that's a - <span class="emphasis"><em>lot</em></span> of state. - </p><p> - You can then keep track of the <span class="quote">“<span class="quote">maximum bit used</span>”</span> - 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.) - </p><p> - <span class="emphasis"><em>A container<bool>. </em></span> 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 class="code">Container<char></code> or - <code class="code">Container<short int></code>. Specifically, - <code class="code">vector<bool></code> is required to be specialized for - that space savings. - </p><p> - The problem is that <code class="code">vector<bool></code> doesn't - behave like a normal vector anymore. There have been - 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 class="code">vector<bool></code> - specialization. In the meantime, <code class="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). - </p><p> - <span class="emphasis"><em>Extremely weird solutions. </em></span> 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 class="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 class="code">bitset<N></code> for the exact - <code class="code">N</code> that you need at the time. Don't forget to delete - the temporary files. (Yes, this <span class="emphasis"><em>can</em></span> be, and - <span class="emphasis"><em>has been</em></span>, done.) - </p><p> - This would be the approach of either a visionary genius or a - raving lunatic, depending on your programming and management - style. Probably the latter. - </p><p> - 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... - </p><p> - Also note that the implementation of bitset used in libstdc++ has - <a class="link" href="ext_containers.html#manual.ext.containers.sgi" title="Backwards Compatibility">some extensions</a>. - </p></div><div class="section"><div class="titlepage"><div><div><h4 class="title"><a id="associative.bitset.type_string"></a>Type String</h4></div></div></div><p> - </p><p> - 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 <span class="quote">“<span class="quote">Links</span>”</span> from - the homepage, and from the C++ information <span class="quote">“<span class="quote">defect - reflector</span>”</span> link, select the library issues list. Issue - number 116 describes the problem. - </p><p> - For now you can simply make a temporary string object using the - constructor expression: - </p><pre class="programlisting"> - std::bitset<5> b ( std::string(<span class="quote">“<span class="quote">10110</span>”</span>) ); - </pre><p> - instead of - </p><pre class="programlisting"> - std::bitset<5> b ( <span class="quote">“<span class="quote">10110</span>”</span> ); // invalid - </pre></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="containers.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="containers.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="unordered_associative.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 9. - Containers - - </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Unordered Associative</td></tr></table></div></body></html>
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