1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>try_ catch_ Statement</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. Phoenix 3.2.0"> 8<link rel="up" href="../statement.html" title="Statement"> 9<link rel="prev" href="for_statement.html" title="for_ Statement"> 10<link rel="next" href="throw_.html" title="throw_"> 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="for_statement.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../statement.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="throw_.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h4 class="title"> 27<a name="phoenix.modules.statement.try__catch__statement"></a><a class="link" href="try__catch__statement.html" title="try_ catch_ Statement">try_ 28 catch_ Statement</a> 29</h4></div></div></div> 30<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">phoenix</span><span class="special">/</span><span class="identifier">statement</span><span class="special">/</span><span class="identifier">try_catch</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 31</pre> 32<p> 33 The syntax is: 34 </p> 35<pre class="programlisting"><span class="identifier">try_</span> 36<span class="special">[</span> 37 <span class="identifier">sequenced_statements</span> 38<span class="special">]</span> 39<span class="special">.</span><span class="identifier">catch_</span><span class="special"><</span><span class="identifier">exception_type</span><span class="special">>()</span> 40<span class="special">[</span> 41 <span class="identifier">sequenced_statements</span> 42<span class="special">]</span> 43<span class="special">.</span><span class="identifier">catch_</span><span class="special"><</span><span class="identifier">another_exception_type</span><span class="special">>(</span><span class="identifier">local</span><span class="special">-</span><span class="identifier">id</span><span class="special">)</span> 44<span class="special">[</span> 45 <span class="identifier">sequenced_statements</span> 46<span class="special">]</span> 47<span class="special">...</span> 48<span class="special">.</span><span class="identifier">catch_all</span> 49<span class="special">[</span> 50 <span class="identifier">sequenced_statement</span> 51<span class="special">]</span> 52</pre> 53<p> 54 Note the usual underscore after try and catch, and the extra parentheses 55 required after the catch. 56 </p> 57<p> 58 The second form of catch statement can refer thrown exception using specified 59 local-id, which is <a class="link" href="../scope/local_variables.html" title="Local Variables">Local 60 Variables</a>, in sequenced_statements. 61 </p> 62<p> 63 Example: The following code calls the (lazy) function <code class="computeroutput"><span class="identifier">f</span></code> 64 for each element, and prints messages about different exception types it 65 catches. 66 </p> 67<pre class="programlisting"><span class="identifier">try_</span> 68<span class="special">[</span> 69 <span class="identifier">f</span><span class="special">(</span><span class="identifier">arg1</span><span class="special">)</span> 70<span class="special">]</span> 71<span class="special">.</span><span class="identifier">catch_</span><span class="special"><</span><span class="identifier">runtime_error</span><span class="special">>()</span> 72<span class="special">[</span> 73 <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">val</span><span class="special">(</span><span class="string">"caught runtime error or derived\n"</span><span class="special">)</span> 74<span class="special">]</span> 75<span class="special">.</span><span class="identifier">catch_</span><span class="special"><</span><span class="identifier">exception</span><span class="special">>(</span><span class="identifier">e_</span><span class="special">)</span> 76<span class="special">[</span> 77 <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">val</span><span class="special">(</span><span class="string">"caught exception or derived: "</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">bind</span><span class="special">(&</span><span class="identifier">exception</span><span class="special">::</span><span class="identifier">what</span><span class="special">,</span> <span class="identifier">e_</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">val</span><span class="special">(</span><span class="string">"\n"</span><span class="special">)</span> 78<span class="special">]</span> 79<span class="special">.</span><span class="identifier">catch_all</span> 80<span class="special">[</span> 81 <span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">val</span><span class="special">(</span><span class="string">"caught some other type of exception\n"</span><span class="special">)</span> 82<span class="special">]</span> 83</pre> 84</div> 85<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 86<td align="left"></td> 87<td align="right"><div class="copyright-footer">Copyright © 2002-2005, 2010, 2014, 2015 Joel de Guzman, Dan Marsden, Thomas 88 Heller, John Fletcher<p> 89 Distributed under the Boost Software License, Version 1.0. (See accompanying 90 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>) 91 </p> 92</div></td> 93</tr></table> 94<hr> 95<div class="spirit-nav"> 96<a accesskey="p" href="for_statement.html"><img src="../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../statement.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="throw_.html"><img src="../../../../../../../doc/src/images/next.png" alt="Next"></a> 97</div> 98</body> 99</html> 100
