1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Quick Start</title> 5<link rel="stylesheet" href="../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../index.html" title="Chapter 1. Fusion 2.2"> 8<link rel="up" href="../index.html" title="Chapter 1. Fusion 2.2"> 9<link rel="prev" href="introduction.html" title="Introduction"> 10<link rel="next" href="organization.html" title="Organization"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="introduction.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="organization.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h2 class="title" style="clear: both"> 27<a name="fusion.quick_start"></a><a class="link" href="quick_start.html" title="Quick Start">Quick Start</a> 28</h2></div></div></div> 29<p> 30 I assume the reader is already familiar with tuples (<a href="http://www.boost.org/libs/tuple" target="_top">Boost.Tuple</a>) 31 and its ancestor <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span></code>. The tuple is a generalization of <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span></code> 32 for multiple heterogeneous elements (triples, quadruples, etc.). The tuple 33 is more or less a synonym for fusion's <code class="computeroutput"><a class="link" href="container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a></code>. 34 </p> 35<p> 36 For starters, we shall include all of Fusion's <a class="link" href="sequence.html" title="Sequence">Sequence</a>(s) 37 <a href="#ftn.fusion.quick_start.f0" class="footnote" name="fusion.quick_start.f0"><sup class="footnote">[2]</sup></a>: 38 </p> 39<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">sequence</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 40<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">sequence</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 41</pre> 42<p> 43 Let's begin with a <code class="computeroutput"><a class="link" href="container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a></code> <a href="#ftn.fusion.quick_start.f1" class="footnote" name="fusion.quick_start.f1"><sup class="footnote">[3]</sup></a>: 44 </p> 45<pre class="programlisting"><a class="link" href="container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a><span class="special"><</span><span class="keyword">int</span><span class="special">,</span> <span class="keyword">char</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">></span> <span class="identifier">stuff</span><span class="special">(</span><span class="number">1</span><span class="special">,</span> <span class="char">'x'</span><span class="special">,</span> <span class="string">"howdy"</span><span class="special">);</span> 46<span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <a class="link" href="sequence/intrinsic/functions/at_c.html" title="at_c"><code class="computeroutput"><span class="identifier">at_c</span></code></a><span class="special"><</span><span class="number">0</span><span class="special">>(</span><span class="identifier">stuff</span><span class="special">);</span> 47<span class="keyword">char</span> <span class="identifier">ch</span> <span class="special">=</span> <a class="link" href="sequence/intrinsic/functions/at_c.html" title="at_c"><code class="computeroutput"><span class="identifier">at_c</span></code></a><span class="special"><</span><span class="number">1</span><span class="special">>(</span><span class="identifier">stuff</span><span class="special">);</span> 48<span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">s</span> <span class="special">=</span> <a class="link" href="sequence/intrinsic/functions/at_c.html" title="at_c"><code class="computeroutput"><span class="identifier">at_c</span></code></a><span class="special"><</span><span class="number">2</span><span class="special">>(</span><span class="identifier">stuff</span><span class="special">);</span> 49</pre> 50<p> 51 Just replace <code class="computeroutput"><span class="identifier">tuple</span></code> for <code class="computeroutput"><a class="link" href="container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a></code> 52 and <code class="computeroutput"><span class="identifier">get</span></code> for <code class="computeroutput"><a class="link" href="sequence/intrinsic/functions/at_c.html" title="at_c"><code class="computeroutput"><span class="identifier">at_c</span></code></a></code> and this is exactly like 53 <a href="http://www.boost.org/libs/tuple" target="_top">Boost.Tuple</a>. Actually, 54 either names can be used interchangeably. Yet, the similarity ends there. You 55 can do a lot more with Fusion <code class="computeroutput"><a class="link" href="container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a></code> or <code class="computeroutput"><span class="identifier">tuple</span></code>. 56 Let's see some examples. 57 </p> 58<h4> 59<a name="fusion.quick_start.h0"></a> 60 <span class="phrase"><a name="fusion.quick_start.print_the_vector_as_xml"></a></span><a class="link" href="quick_start.html#fusion.quick_start.print_the_vector_as_xml">Print 61 the vector as XML</a> 62 </h4> 63<p> 64 First, let's include the algorithms: 65 </p> 66<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">algorithm</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 67<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">fusion</span><span class="special">/</span><span class="identifier">include</span><span class="special">/</span><span class="identifier">algorithm</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 68</pre> 69<p> 70 Now, let's write a function object that prints XML of the form <type>data</type> 71 for each member in the tuple. 72 </p> 73<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">print_xml</span> 74<span class="special">{</span> 75 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">T</span><span class="special">></span> 76 <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">x</span><span class="special">)</span> <span class="keyword">const</span> 77 <span class="special">{</span> 78 <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> 79 <span class="special"><<</span> <span class="char">'<'</span> <span class="special"><<</span> <span class="keyword">typeid</span><span class="special">(</span><span class="identifier">x</span><span class="special">).</span><span class="identifier">name</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'>'</span> 80 <span class="special"><<</span> <span class="identifier">x</span> 81 <span class="special"><<</span> <span class="string">"</"</span> <span class="special"><<</span> <span class="keyword">typeid</span><span class="special">(</span><span class="identifier">x</span><span class="special">).</span><span class="identifier">name</span><span class="special">()</span> <span class="special"><<</span> <span class="char">'>'</span> 82 <span class="special">;</span> 83 <span class="special">}</span> 84<span class="special">};</span> 85</pre> 86<p> 87 Now, finally: 88 </p> 89<pre class="programlisting"><a class="link" href="algorithm/iteration/functions/for_each.html" title="for_each"><code class="computeroutput"><span class="identifier">for_each</span></code></a><span class="special">(</span><span class="identifier">stuff</span><span class="special">,</span> <span class="identifier">print_xml</span><span class="special">());</span> 90</pre> 91<p> 92 That's it! <code class="computeroutput"><a class="link" href="algorithm/iteration/functions/for_each.html" title="for_each"><code class="computeroutput"><span class="identifier">for_each</span></code></a></code> is a fusion algorithm. 93 It is a generic algorithm similar to <a href="http://en.wikipedia.org/wiki/Standard_Template_Library" target="_top">STL</a>'s. 94 It iterates over the sequence and calls a user supplied function. In our case, 95 it calls <code class="computeroutput"><span class="identifier">print_xml</span></code>'s <code class="computeroutput"><span class="keyword">operator</span><span class="special">()</span></code> for 96 each element in <code class="computeroutput"><span class="identifier">stuff</span></code>. 97 </p> 98<div class="caution"><table border="0" summary="Caution"> 99<tr> 100<td rowspan="2" align="center" valign="top" width="25"><img alt="[Caution]" src="../../../../../doc/src/images/caution.png"></td> 101<th align="left">Caution</th> 102</tr> 103<tr><td align="left" valign="top"><p> 104 The result of <code class="computeroutput"><span class="keyword">typeid</span><span class="special">(</span><span class="identifier">x</span><span class="special">).</span><span class="identifier">name</span><span class="special">()</span></code> is platform specific. The code here is 105 just for exposition. Of course you already know that :-) 106 </p></td></tr> 107</table></div> 108<p> 109 <code class="computeroutput"><a class="link" href="algorithm/iteration/functions/for_each.html" title="for_each"><code class="computeroutput"><span class="identifier">for_each</span></code></a></code> is generic. With 110 <code class="computeroutput"><span class="identifier">print_xml</span></code>, you can use it to 111 print just about any Fusion <a class="link" href="sequence.html" title="Sequence">Sequence</a>. 112 </p> 113<h4> 114<a name="fusion.quick_start.h1"></a> 115 <span class="phrase"><a name="fusion.quick_start.print_only_pointers"></a></span><a class="link" href="quick_start.html#fusion.quick_start.print_only_pointers">Print 116 only pointers</a> 117 </h4> 118<p> 119 Let's get a little cleverer. Say we wish to write a <span class="emphasis"><em>generic</em></span> 120 function that takes in an arbitrary sequence and XML prints only those elements 121 which are pointers. Ah, easy. First, let's include the <code class="computeroutput"><span class="identifier">is_pointer</span></code> 122 boost type trait: 123 </p> 124<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">type_traits</span><span class="special">/</span><span class="identifier">is_pointer</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 125</pre> 126<p> 127 Then, simply: 128 </p> 129<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Sequence</span><span class="special">></span> 130<span class="keyword">void</span> <span class="identifier">xml_print_pointers</span><span class="special">(</span><span class="identifier">Sequence</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">seq</span><span class="special">)</span> 131<span class="special">{</span> 132 <a class="link" href="algorithm/iteration/functions/for_each.html" title="for_each"><code class="computeroutput"><span class="identifier">for_each</span></code></a><span class="special">(</span><a class="link" href="algorithm/transformation/functions/filter_if.html" title="filter_if"><code class="computeroutput"><span class="identifier">filter_if</span></code></a><span class="special"><</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_pointer</span><span class="special"><</span><span class="identifier">_</span><span class="special">></span> <span class="special">>(</span><span class="identifier">seq</span><span class="special">),</span> <span class="identifier">print_xml</span><span class="special">());</span> 133<span class="special">}</span> 134</pre> 135<p> 136 <code class="computeroutput"><a class="link" href="algorithm/transformation/functions/filter_if.html" title="filter_if"><code class="computeroutput"><span class="identifier">filter_if</span></code></a></code> is another Fusion 137 algorithm. It returns a <a class="link" href="view/filter_view.html" title="filter_view"><code class="computeroutput"><span class="identifier">filter_view</span></code></a>, a conforming Fusion sequence. 138 This view reflects only those elements that pass the given predicate. In this 139 case, the predicate is <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">is_pointer</span><span class="special"><</span><span class="identifier">_</span><span class="special">></span></code>. 140 This "filtered view" is then passed to the <a class="link" href="algorithm/iteration/functions/for_each.html" title="for_each"><code class="computeroutput"><span class="identifier">for_each</span></code></a> algorithm, which then prints 141 the "filtered view" as XML. 142 </p> 143<p> 144 Easy, right? 145 </p> 146<h4> 147<a name="fusion.quick_start.h2"></a> 148 <span class="phrase"><a name="fusion.quick_start.associative_tuples"></a></span><a class="link" href="quick_start.html#fusion.quick_start.associative_tuples">Associative 149 tuples</a> 150 </h4> 151<p> 152 Ok, moving on... 153 </p> 154<p> 155 Apart from <code class="computeroutput"><a class="link" href="container/vector.html" title="vector"><code class="computeroutput"><span class="identifier">vector</span></code></a></code>, 156 fusion has a couple of other sequence types to choose from. Each sequence has 157 its own characteristics. We have <code class="computeroutput"><a class="link" href="container/list.html" title="list"><code class="computeroutput"><span class="identifier">list</span></code></a></code>, <code class="computeroutput"><a class="link" href="container/set.html" title="set"><code class="computeroutput"><span class="identifier">set</span></code></a></code>, <code class="computeroutput"><a class="link" href="container/map.html" title="map"><code class="computeroutput"><span class="identifier">map</span></code></a></code>, plus a multitude of <code class="computeroutput"><span class="identifier">views</span></code> that provide various ways to present 158 the sequences. 159 </p> 160<p> 161 Fusion's <code class="computeroutput"><a class="link" href="container/map.html" title="map"><code class="computeroutput"><span class="identifier">map</span></code></a></code> 162 associate types with elements. It can be used as a cleverer replacement of 163 the <code class="computeroutput"><span class="keyword">struct</span></code>. Example: 164 </p> 165<pre class="programlisting"><span class="keyword">namespace</span> <span class="identifier">fields</span> 166<span class="special">{</span> 167 <span class="keyword">struct</span> <span class="identifier">name</span><span class="special">;</span> 168 <span class="keyword">struct</span> <span class="identifier">age</span><span class="special">;</span> 169<span class="special">}</span> 170 171<span class="keyword">typedef</span> <a class="link" href="container/map.html" title="map"><code class="computeroutput"><span class="identifier">map</span></code></a><span class="special"><</span> 172 <a class="link" href="support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">fusion</span><span class="special">::</span><span class="identifier">pair</span></code></a><span class="special"><</span><span class="identifier">fields</span><span class="special">::</span><span class="identifier">name</span><span class="special">,</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">></span> 173 <span class="special">,</span> <a class="link" href="support/pair.html" title="pair"><code class="computeroutput"><span class="identifier">fusion</span><span class="special">::</span><span class="identifier">pair</span></code></a><span class="special"><</span><span class="identifier">fields</span><span class="special">::</span><span class="identifier">age</span><span class="special">,</span> <span class="keyword">int</span><span class="special">></span> <span class="special">></span> 174<span class="identifier">person</span><span class="special">;</span> 175</pre> 176<p> 177 <code class="computeroutput"><a class="link" href="container/map.html" title="map"><code class="computeroutput"><span class="identifier">map</span></code></a></code> 178 is an associative sequence. Its elements are Fusion pairs which differ somewhat 179 from <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span></code>. Fusion pairs only contain one member, 180 with the type of their second template parameter. The first type parameter 181 of the pair is used as an index to the associated element in the sequence. 182 For example, given a <code class="computeroutput"><span class="identifier">a_person</span></code> 183 of type, <code class="computeroutput"><span class="identifier">person</span></code>, you can do: 184 </p> 185<pre class="programlisting"><span class="keyword">using</span> <span class="keyword">namespace</span> <span class="identifier">fields</span><span class="special">;</span> 186<span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">person_name</span> <span class="special">=</span> <a class="link" href="sequence/intrinsic/functions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">at_key</span></code></a><span class="special"><</span><span class="identifier">name</span><span class="special">>(</span><span class="identifier">a_person</span><span class="special">);</span> 187<span class="keyword">int</span> <span class="identifier">person_age</span> <span class="special">=</span> <a class="link" href="sequence/intrinsic/functions/at_key.html" title="at_key"><code class="computeroutput"><span class="identifier">at_key</span></code></a><span class="special"><</span><span class="identifier">age</span><span class="special">>(</span><span class="identifier">a_person</span><span class="special">);</span> 188</pre> 189<p> 190 Why go through all this trouble, you say? Well, for one, unlike the <code class="computeroutput"><span class="keyword">struct</span></code>, we are dealing with a generic data structure. 191 There are a multitude of facilities available at your disposal provided out 192 of the box with fusion or written by others. With these facilities, introspection 193 comes for free, for example. We can write one serialization function (well, 194 two, if you consider loading and saving) that will work for all your fusion 195 <code class="computeroutput"><a class="link" href="container/map.html" title="map"><code class="computeroutput"><span class="identifier">map</span></code></a></code>s. 196 Example: 197 </p> 198<pre class="programlisting"><span class="keyword">struct</span> <span class="identifier">saver</span> 199<span class="special">{</span> 200 <span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Pair</span><span class="special">></span> 201 <span class="keyword">void</span> <span class="keyword">operator</span><span class="special">()(</span><span class="identifier">Pair</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">data</span><span class="special">)</span> <span class="keyword">const</span> 202 <span class="special">{</span> 203 <span class="identifier">some_archive</span> <span class="special"><<</span> <span class="identifier">data</span><span class="special">.</span><span class="identifier">second</span><span class="special">;</span> 204 <span class="special">}</span> 205<span class="special">};</span> 206 207<span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Stuff</span><span class="special">></span> 208<span class="keyword">void</span> <span class="identifier">save</span><span class="special">(</span><span class="identifier">Stuff</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">stuff</span><span class="special">)</span> 209<span class="special">{</span> 210 <a class="link" href="algorithm/iteration/functions/for_each.html" title="for_each"><code class="computeroutput"><span class="identifier">for_each</span></code></a><span class="special">(</span><span class="identifier">stuff</span><span class="special">,</span> <span class="identifier">saver</span><span class="special">());</span> 211<span class="special">}</span> 212</pre> 213<p> 214 The <code class="computeroutput"><span class="identifier">save</span></code> function is generic 215 and will work for all types of <code class="computeroutput"><span class="identifier">stuff</span></code> 216 regardless if it is a <code class="computeroutput"><span class="identifier">person</span></code>, 217 a <code class="computeroutput"><span class="identifier">dog</span></code> or a whole <code class="computeroutput"><span class="identifier">alternate_universe</span></code>. 218 </p> 219<h4> 220<a name="fusion.quick_start.h3"></a> 221 <span class="phrase"><a name="fusion.quick_start.tip_of_the_iceberg"></a></span><a class="link" href="quick_start.html#fusion.quick_start.tip_of_the_iceberg">Tip 222 of the Iceberg</a> 223 </h4> 224<p> 225 And... we've barely scratched the surface! You can compose and expand the data 226 structures, remove elements from the structures, find specific data types, 227 query the elements, filter out types for inspection, transform data structures, 228 etc. What you've seen is just the tip of the iceberg. 229 </p> 230<div class="footnotes"> 231<br><hr style="width:100; text-align:left;margin-left: 0"> 232<div id="ftn.fusion.quick_start.f0" class="footnote"><p><a href="#fusion.quick_start.f0" class="para"><sup class="para">[2] </sup></a> 233 There are finer grained header files available if you wish to have more control 234 over which components to include (see section <a class="link" href="organization.html" title="Organization">Organization</a> 235 for details). 236 </p></div> 237<div id="ftn.fusion.quick_start.f1" class="footnote"><p><a href="#fusion.quick_start.f1" class="para"><sup class="para">[3] </sup></a> 238 Unless otherwise noted, components are in namespace <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">fusion</span></code>. 239 For the sake of simplicity, code in this quick start implies <code class="computeroutput"><span class="keyword">using</span></code> directives for the fusion components 240 we will be using. 241 </p></div> 242</div> 243</div> 244<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 245<td align="left"></td> 246<td align="right"><div class="copyright-footer">Copyright © 2001-2006, 2011, 2012 Joel de Guzman, 247 Dan Marsden, Tobias Schwinger<p> 248 Distributed under the Boost Software License, Version 1.0. (See accompanying 249 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 250 </p> 251</div></td> 252</tr></table> 253<hr> 254<div class="spirit-nav"> 255<a accesskey="p" href="introduction.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../index.html"><img src="../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../index.html"><img src="../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="organization.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 256</div> 257</body> 258</html> 259
