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diff --git a/libstdc++-v3/doc/html/manual/using_namespaces.html b/libstdc++-v3/doc/html/manual/using_namespaces.html new file mode 100644 index 000000000..ffd6c6f63 --- /dev/null +++ b/libstdc++-v3/doc/html/manual/using_namespaces.html @@ -0,0 +1,61 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"><head><title>Namespaces</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"/><meta name="keywords" content=" ISO C++ , library "/><link rel="home" href="../spine.html" title="The GNU C++ Library"/><link rel="up" href="using.html" title="Chapter 3. Using"/><link rel="prev" href="using_macros.html" title="Macros"/><link rel="next" href="using_dynamic_or_shared.html" title="Linking"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Namespaces</th></tr><tr><td align="left"><a accesskey="p" href="using_macros.html">Prev</a> </td><th width="60%" align="center">Chapter 3. Using</th><td align="right"> <a accesskey="n" href="using_dynamic_or_shared.html">Next</a></td></tr></table><hr/></div><div class="section" title="Namespaces"><div class="titlepage"><div><div><h2 class="title"><a id="manual.intro.using.namespaces"/>Namespaces</h2></div></div></div><div class="section" title="Available Namespaces"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.namespaces.all"/>Available Namespaces</h3></div></div></div><p> There are three main namespaces. +</p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p>std</p><p>The ISO C++ standards specify that "all library entities are defined +within namespace std." This includes namespaces nested +within <code class="code">namespace std</code>, such as <code class="code">namespace +std::tr1</code>. +</p></li><li class="listitem"><p>abi</p><p>Specified by the C++ ABI. This ABI specifies a number of type and +function APIs supplemental to those required by the ISO C++ Standard, +but necessary for interoperability. +</p></li><li class="listitem"><p>__gnu_</p><p>Indicating one of several GNU extensions. Choices +include <code class="code">__gnu_cxx</code>, <code class="code">__gnu_debug</code>, <code class="code">__gnu_parallel</code>, +and <code class="code">__gnu_pbds</code>. +</p></li></ul></div><p> A complete list of implementation namespaces (including namespace contents) is available in the generated source <a class="link" href="http://gcc.gnu.org/onlinedocs/libstdc++/latest-doxygen/namespaces.html">documentation</a>. +</p></div><div class="section" title="namespace std"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.namespaces.std"/>namespace std</h3></div></div></div><p> + One standard requirement is that the library components are defined + in <code class="code">namespace std::</code>. Thus, in order to use these types or + functions, one must do one of two things: +</p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p>put a kind of <span class="emphasis"><em>using-declaration</em></span> in your source +(either <code class="code">using namespace std;</code> or i.e. <code class="code">using +std::string;</code>) This approach works well for individual source files, but +should not be used in a global context, like header files. + </p></li><li class="listitem"><p>use a <span class="emphasis"><em>fully +qualified name</em></span> for each library symbol +(i.e. <code class="code">std::string</code>, <code class="code">std::cout</code>) Always can be +used, and usually enhanced, by strategic use of typedefs. (In the +cases where the qualified verbiage becomes unwieldy.) + </p></li></ul></div></div><div class="section" title="Using Namespace Composition"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.namespaces.comp"/>Using Namespace Composition</h3></div></div></div><p> +Best practice in programming suggests sequestering new data or +functionality in a sanely-named, unique namespace whenever +possible. This is considered an advantage over dumping everything in +the global namespace, as then name look-up can be explicitly enabled or +disabled as above, symbols are consistently mangled without repetitive +naming prefixes or macros, etc. +</p><p>For instance, consider a project that defines most of its classes in <code class="code">namespace gtk</code>. It is possible to + adapt <code class="code">namespace gtk</code> to <code class="code">namespace std</code> by using a C++-feature called + <span class="emphasis"><em>namespace composition</em></span>. This is what happens if + a <span class="emphasis"><em>using</em></span>-declaration is put into a + namespace-definition: the imported symbol(s) gets imported into the + currently active namespace(s). For example: +</p><pre class="programlisting"> +namespace gtk +{ + using std::string; + using std::tr1::array; + + class Window { ... }; +} +</pre><p> + In this example, <code class="code">std::string</code> gets imported into + <code class="code">namespace gtk</code>. The result is that use of + <code class="code">std::string</code> inside namespace gtk can just use <code class="code">string</code>, without the explicit qualification. + As an added bonus, + <code class="code">std::string</code> does not get imported into + the global namespace. Additionally, a more elaborate arrangement can be made for backwards compatibility and portability, whereby the + <code class="code">using</code>-declarations can wrapped in macros that + are set based on autoconf-tests to either "" or i.e. <code class="code">using + std::string;</code> (depending on whether the system has + libstdc++ in <code class="code">std::</code> or not). (ideas from + Llewelly and Karl Nelson) +</p></div></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td align="left"><a accesskey="p" href="using_macros.html">Prev</a> </td><td align="center"><a accesskey="u" href="using.html">Up</a></td><td align="right"> <a accesskey="n" href="using_dynamic_or_shared.html">Next</a></td></tr><tr><td align="left" valign="top">Macros </td><td align="center"><a accesskey="h" href="../spine.html">Home</a></td><td align="right" valign="top"> Linking</td></tr></table></div></body></html> |