30 lines
6.5 KiB
HTML
30 lines
6.5 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>The Be Book - System Overview - The Support Kit</title><link rel="stylesheet" href="be_book.css" type="text/css" media="all" /><link rel="shortcut icon" type="image/vnd.microsoft.icon" href="./images/favicon.ico" /><!--[if IE]>
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<link rel="stylesheet" type="text/css" href="be_book_ie.css" />
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<![endif]--><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /><meta name="keywords" content="Access, BeOS, BeBook, API" /><link rel="start" href="index.html" title="The Be Book" /><link rel="up" href="TheSupportKit_Overview.html" title="The Support Kit" /><link rel="prev" href="BFlattenable_Overview.html" title="BFlattenable" /><link rel="next" href="BLocker_Overview.html" title="BLocker" /></head><body><div id="header"><div id="headerT"><div id="headerTL"><a accesskey="p" href="BFlattenable_Overview.html" title="BFlattenable"><img src="./images/navigation/prev.png" alt="Prev" /></a> <a accesskey="u" href="TheSupportKit_Overview.html" title="The Support Kit"><img src="./images/navigation/up.png" alt="Up" /></a> <a accesskey="n" href="BLocker_Overview.html" title="BLocker"><img src="./images/navigation/next.png" alt="Next" /></a></div><div id="headerTR"><div id="navigpeople"><a href="http://www.haiku-os.org"><img src="./images/People_24.png" alt="haiku-os.org" title="Visit The Haiku Website" /></a></div><div class="navighome" title="Home"><a accesskey="h" href="index.html"><img src="./images/navigation/home.png" alt="Home" /></a></div><div class="navigboxed" id="navigindex"><a accesskey="i" href="ClassIndex.html" title="Index">I</a></div><div class="navigboxed" id="naviglang" title="English">en</div></div><div id="headerTC">The Be Book - System Overview - The Support Kit</div></div><div id="headerB">Prev: <a href="BFlattenable_Overview.html">BFlattenable</a> Up: <a href="TheSupportKit_Overview.html">The Support Kit</a> Next: <a href="BLocker_Overview.html">BLocker</a></div><hr /></div><div class="section"><div xmlns="" xmlns:d="http://docbook.org/ns/docbook" class="titlepage"><div><div xmlns:d="http://docbook.org/ns/docbook"><h2 xmlns="http://www.w3.org/1999/xhtml" class="title"><a id="BList_Overview"></a>BList</h2></div></div></div><a id="id618646" class="indexterm"></a><p>A <a class="link" href="BList.html" title="BList"><code class="classname">BList</code></a>
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object is a compact, ordered list of data pointers.
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<a class="link" href="BList.html" title="BList"><code class="classname">BList</code></a> objects
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can contain pointers to any type of data, including—and
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especially—objects.</p><p>An item assigned to a
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<a class="link" href="BList.html" title="BList"><code class="classname">BList</code></a>
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is identified by an index to its position in
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the list. Indices start at 0 and are neither arbitrary nor permanent. If,
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for example, you insert an item into the middle of a list, the indices of
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the items at the tail of the list are incremented (by one). Similarly,
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removing an item decrements the indices of the following items.</p><p>A <a class="link" href="BList.html" title="BList"><code class="classname">BList</code></a>
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stores its items as type <span class="type">void*</span>, so it's necessary to cast an
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item to the correct type when you retrieve it. For example, items
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retrieved from a list of
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<a class="link" href="BBitmap.html" title="BBitmap"><code class="classname">BBitmap</code></a>
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objects must be cast as
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<a class="link" href="BBitmap.html" title="BBitmap"><code class="classname">BBitmap</code></a> pointers:</p><pre class="programlisting example cpp"><code class="classname">BBitmap</code> *<code class="varname">theImage</code> = (<code class="classname">BBitmap</code> *)<code class="varname">myList</code>-><code class="methodname">ItemAt</code>(<code class="varname">anIndex</code>);</pre><div class="admonition warning"><div class="title">Warning</div><div class="graphic"><img class="icon" alt="Warning" width="32" src="./images/admonitions/Stop_32.png" /><div class="text"><p>There's nothing to prevent you from adding a <code class="constant">NULL</code>
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pointer to a <a class="link" href="BList.html" title="BList"><code class="classname">BList</code></a>.
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However, functions that retrieve items from the list (such as
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<a class="link" href="BList.html#BList_ItemAt" title="ItemAt()"><code class="methodname">ItemAt()</code></a>)
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return <code class="constant">NULL</code> when the requested item can't be found. Thus, you can't
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distinguish between a valid <code class="constant">NULL</code> item and an invalid attempt to access an
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item that isn't there.</p></div></div></div></div><div id="footer"><hr /><div id="footerT">Prev: <a href="BFlattenable_Overview.html">BFlattenable</a> Up: <a href="TheSupportKit_Overview.html">The Support Kit</a> Next: <a href="BLocker_Overview.html">BLocker</a> </div><div id="footerB"><div id="footerBL"><a href="BFlattenable_Overview.html" title="BFlattenable"><img src="./images/navigation/prev.png" alt="Prev" /></a> <a href="TheSupportKit_Overview.html" title="The Support Kit"><img src="./images/navigation/up.png" alt="Up" /></a> <a href="BLocker_Overview.html" title="BLocker"><img src="./images/navigation/next.png" alt="Next" /></a></div><div id="footerBR"><div><a href="http://www.haiku-os.org"><img src="./images/People_24.png" alt="haiku-os.org" title="Visit The Haiku Website" /></a></div><div class="navighome" title="Home"><a accesskey="h" href="index.html"><img src="./images/navigation/home.png" alt="Home" /></a></div></div><div id="footerBC"><a href="http://www.access-company.com/home.html" title="ACCESS Co."><img alt="Access Company" src="./images/access_logo.png" /></a></div></div></div><div id="licenseFooter"><div id="licenseFooterBL"><a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/" title="Creative Commons License"><img alt="Creative Commons License" style="border-width:0" src="https://licensebuttons.net/l/by-nc-nd/3.0/88x31.png" /></a></div><div id="licenseFooterBR"><a href="./LegalNotice.html">Legal Notice</a></div><div id="licenseFooterBC"><span id="licenseText">This work is licensed under a
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<a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative
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Commons Attribution-Non commercial-No Derivative Works 3.0 License</a>.</span></div></div></body></html>
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