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diff --git a/share/doc/gcc/Fast-enumeration-details.html b/share/doc/gcc/Fast-enumeration-details.html new file mode 100644 index 0000000..ed5e20c --- /dev/null +++ b/share/doc/gcc/Fast-enumeration-details.html @@ -0,0 +1,143 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- This file documents the use of the GNU compilers. + +Copyright (C) 1988-2023 Free Software Foundation, Inc. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with the +Invariant Sections being "Funding Free Software", the Front-Cover +Texts being (a) (see below), and with the Back-Cover Texts being (b) +(see below). A copy of the license is included in the section entitled +"GNU Free Documentation License". + +(a) The FSF's Front-Cover Text is: + +A GNU Manual + +(b) The FSF's Back-Cover Text is: + +You have freedom to copy and modify this GNU Manual, like GNU + software. Copies published by the Free Software Foundation raise + funds for GNU development. --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>Using the GNU Compiler Collection (GCC): Fast enumeration details</title> + +<meta name="description" content="Using the GNU Compiler Collection (GCC): Fast enumeration details"> +<meta name="keywords" content="Using the GNU Compiler Collection (GCC): Fast enumeration details"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Indices.html#Indices" rel="index" title="Indices"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Fast-enumeration.html#Fast-enumeration" rel="up" title="Fast enumeration"> +<link href="Fast-enumeration-protocol.html#Fast-enumeration-protocol" rel="next" title="Fast enumeration protocol"> +<link href="c99_002dlike-fast-enumeration-syntax.html#c99_002dlike-fast-enumeration-syntax" rel="previous" title="c99-like fast enumeration syntax"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +div.smalllisp {margin-left: 3.2em} +kbd {font-style:oblique} +pre.display {font-family: inherit} +pre.format {font-family: inherit} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en_US" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Fast-enumeration-details"></a> +<div class="header"> +<p> +Next: <a href="Fast-enumeration-protocol.html#Fast-enumeration-protocol" accesskey="n" rel="next">Fast enumeration protocol</a>, Previous: <a href="c99_002dlike-fast-enumeration-syntax.html#c99_002dlike-fast-enumeration-syntax" accesskey="p" rel="previous">c99-like fast enumeration syntax</a>, Up: <a href="Fast-enumeration.html#Fast-enumeration" accesskey="u" rel="up">Fast enumeration</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="Fast-Enumeration-Details"></a> +<h4 class="subsection">8.9.3 Fast Enumeration Details</h4> + +<p>Here is a more technical description with the gory details. Consider the code +</p> +<div class="smallexample"> +<pre class="smallexample"> for (<var>object expression</var> in <var>collection expression</var>) + { + <var>statements</var> + } +</pre></div> + +<p>here is what happens when you run it: +</p> +<ul> +<li> <code><var>collection expression</var></code> is evaluated exactly once and the +result is used as the collection object to iterate over. This means +it is safe to write code such as <code>for (object in [NSDictionary +keyEnumerator]) …</code>. + +</li><li> the iteration is implemented by the compiler by repeatedly getting +batches of objects from the collection object using the fast +enumeration protocol (see below), then iterating over all objects in +the batch. This is faster than a normal enumeration where objects are +retrieved one by one (hence the name “fast enumeration”). + +</li><li> if there are no objects in the collection, then +<code><var>object expression</var></code> is set to <code>nil</code> and the loop +immediately terminates. + +</li><li> if there are objects in the collection, then for each object in the +collection (in the order they are returned) <code><var>object expression</var></code> +is set to the object, then <code><var>statements</var></code> are executed. + +</li><li> <code><var>statements</var></code> can contain <code>break</code> and <code>continue</code> +commands, which will abort the iteration or skip to the next loop +iteration as expected. + +</li><li> when the iteration ends because there are no more objects to iterate +over, <code><var>object expression</var></code> is set to <code>nil</code>. This allows +you to determine whether the iteration finished because a <code>break</code> +command was used (in which case <code><var>object expression</var></code> will remain +set to the last object that was iterated over) or because it iterated +over all the objects (in which case <code><var>object expression</var></code> will be +set to <code>nil</code>). + +</li><li> <code><var>statements</var></code> must not make any changes to the collection +object; if they do, it is a hard error and the fast enumeration +terminates by invoking <code>objc_enumerationMutation</code>, a runtime +function that normally aborts the program but which can be customized +by Foundation libraries via <code>objc_set_mutation_handler</code> to do +something different, such as raising an exception. + +</li></ul> + +<hr> +<div class="header"> +<p> +Next: <a href="Fast-enumeration-protocol.html#Fast-enumeration-protocol" accesskey="n" rel="next">Fast enumeration protocol</a>, Previous: <a href="c99_002dlike-fast-enumeration-syntax.html#c99_002dlike-fast-enumeration-syntax" accesskey="p" rel="previous">c99-like fast enumeration syntax</a>, Up: <a href="Fast-enumeration.html#Fast-enumeration" accesskey="u" rel="up">Fast enumeration</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Indices.html#Indices" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |