1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" 2"http://www.w3.org/TR/html4/loose.dtd"> 3 4<html> 5<head> 6 <meta http-equiv="Content-Language" content="en-us"> 7 <meta http-equiv="Content-Type" content="text/html; charset=us-ascii"> 8 <link rel="stylesheet" type="text/css" href="../../../../boost.css"> 9 10 <title>Policies</title> 11</head> 12 13<body lang="en"> 14 <h1>Policies</h1> 15 16 <p>The <code>interval</code> template requires two arguments. The first 17 corresponds to the base type chosen for the bounds. And the second defines 18 the <a href="rounding.htm">rounding</a> and <a href= 19 "checking.htm">checking</a> behaviors of the newly constructed class. This 20 second argument is not mandatory but may need some customizations. In order 21 to ease the manipulations, some helper templates are provided in 22 <code>interval/policies.hpp</code>.</p> 23 <pre> 24namespace boost { 25namespace numeric { 26namespace interval_lib { 27 28template<class Rounding, class Checking> 29struct policies { 30 typedef Rounding rounding; 31 typedef Checking checking; 32}; 33 34template<class OldInterval, class NewRounding> 35struct change_rounding { 36 typedef ... type; 37}; 38 39template<class OldInterval, class NewChecking> 40struct change_checking { 41 typedef ... type; 42}; 43 44template<class OldInterval> 45struct unprotect { 46 typedef ... type; 47}; 48 49} // namespace interval_lib 50} // namespace numeric 51} // namespace boost 52</pre> 53 54 <p>The <code>policies</code> template should be used whenever the user 55 needs to define a policy structure for an <code>interval</code> class. 56 <code>change_rounding</code> and <code>change_checking</code> can be used 57 to get the type of a new interval by changing one of the policies of an old 58 interval; the new type is available thanks to the type definition 59 <code>type</code>. Finally, <code>unprotect</code> looks like 60 <code>change_rounding</code> and directly changes the rounding of an 61 interval to its unprotected version (a better explanation is available 62 <a href="rounding.htm#perfexp">here</a>).</p> 63 <hr> 64 65 <p><a href="http://validator.w3.org/check?uri=referer"><img border="0" src= 66 "../../../../doc/images/valid-html401.png" alt="Valid HTML 4.01 Transitional" 67 height="31" width="88"></a></p> 68 69 <p>Revised 70 <!--webbot bot="Timestamp" s-type="EDITED" s-format="%Y-%m-%d" startspan -->2006-12-24<!--webbot bot="Timestamp" endspan i-checksum="12172" --></p> 71 72 <p><i>Copyright © 2002 Guillaume Melquiond, Sylvain Pion, Hervé 73 Brönnimann, Polytechnic University</i></p> 74 75 <p><i>Distributed under the Boost Software License, Version 1.0. (See 76 accompanying file <a href="../../../../LICENSE_1_0.txt">LICENSE_1_0.txt</a> 77 or copy at <a href= 78 "http://www.boost.org/LICENSE_1_0.txt">http://www.boost.org/LICENSE_1_0.txt</a>)</i></p> 79</body> 80</html> 81
