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diff --git a/libstdc++-v3/doc/html/manual/containers_and_c.html b/libstdc++-v3/doc/html/manual/containers_and_c.html new file mode 100644 index 00000000000..512f7a2c5d2 --- /dev/null +++ b/libstdc++-v3/doc/html/manual/containers_and_c.html @@ -0,0 +1,66 @@ +<?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>Chapter 18. Interacting with C</title><meta name="generator" content="DocBook XSL Stylesheets V1.74.0" /><meta name="keywords" content=" ISO C++ , library " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="containers.html" title="Part VII. Containers" /><link rel="prev" href="bitset.html" title="bitset" /><link rel="next" href="iterators.html" title="Part VIII. Iterators" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 18. Interacting with C</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="bitset.html">Prev</a> </td><th width="60%" align="center">Part VII. + Containers + +</th><td width="20%" align="right"> <a accesskey="n" href="iterators.html">Next</a></td></tr></table><hr /></div><div class="chapter" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title"><a id="manual.containers.c"></a>Chapter 18. Interacting with C</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="containers_and_c.html#containers.c.vs_array">Containers vs. Arrays</a></span></dt></dl></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="containers.c.vs_array"></a>Containers vs. Arrays</h2></div></div></div><p> + 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. + </p><p> + 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 “<span class="quote">container</span>” on which they work, since + the algorithms are only given endpoints to work with. For the + container classes, these are iterators (usually + <code class="code">begin()</code> and <code class="code">end()</code>, but not always). + For builtin arrays, these are the address of the first element + and the <a class="ulink" href="../24_iterators/howto.html#2" target="_top">past-the-end</a> element. + </p><p> + Some very simple wrapper functions can hide all of that from the + rest of the code. For example, a pair of functions called + <code class="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 class="code">begin()</code> iterator. + </p><p> + 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 class="code">beginof</code> being optimized out + of existence, so you pay absolutely nothing in terms of increased + code size or execution time. + </p><p> + The result is that if all your algorithm calls look like + </p><pre class="programlisting"> + std::transform(beginof(foo), endof(foo), beginof(foo), SomeFunction); + </pre><p> + 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. + </p><p> + This author has a collection of such functions, called + “<span class="quote">*of</span>” because they all extend the builtin + “<span class="quote">sizeof</span>”. 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 <a class="ulink" href="wrappers_h.txt" target="_top">given here</a>. + </p><p> + Astute readers will notice two things at once: first, that the + container class is still a <code class="code">vector<T></code> instead + of a more general <code class="code">Container<T></code>. This would + mean that three functions for <code class="code">deque</code> would have to be + added, another three for <code class="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. + </p><p> + Second, the line + </p><pre class="programlisting"> + inline unsigned int lengthof (T (&)[sz]) { return sz; } + </pre><p> + looks just weird! Hint: unused parameters can be left nameless. + </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="bitset.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="iterators.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">bitset </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Part VIII. + Iterators + +</td></tr></table></div></body></html> |